For a few moments when I loaded up Metro 2033 Redux I had one of those "Hm, I don't think anything has really changed" reactions. It's been about two years since I last played Metro 2033, and I remembered it looking...well, basically the same as the Redux version looks. Metro 2033 was gorgeous when it came out, so this didn't really surprise me.
Then I swapped back to the original Metro 2033.
Wow. Graphics have come a surprisingly long way in the last four years.
Metro 2033 Redux and Metro: Last Light Redux are the "definitive" or "director's cut" versions of each game. You're receiving a slightly prettier version of each game, complete with all the DLC and some new features—for instance, being able to wipe water/blood off the gas mask in Metro 2033. Surprise! You couldn't do that in 2033, even if your brain is telling you that you could. Wiping the gas mask was a new feature for Metro: Last Light, Metro 2033's sequel.
I didn't play through the entirety of the Redux versions. While I love the Metro series, I have little desire to go back and revisit both games in their entirety, back to back. That being said, I played through the first two hours of each game, and then went back and played through the first forty minutes of the originals to make some comparisons.
I also made use of the game's new mode selection—you can play each game in "Survival Mode" or "Spartan Mode." Survival Mode is supposedly more akin to 2033's survival-horror style pacing, while Spartan Mode emulates Last Light's run-n-gun action by making the player more durable and doling out more ammo. Each game can be played in either mode, so I played 2033 Redux in Spartan Mode and Last Light Redux in Survival Mode just to see what happened.
First off: The graphics. Both games use Last Light's engine, so the difference for Last Light Redux is unnoticeable. I assume the developers touched up a few things here and there, but Last Light's only a year old.
Metro 2033, on the other hand, receives a significant boost. First of all, I rejoiced that 2033 Redux doesn't default to leaving PhysX on. As an AMD user, the original 2033 confused the hell out of me when I first bought it because Nvidia's proprietary PhysX technology was (unbeknownst to me) tanking my system. It's the smallest change possible, but I was excited to see this version rectify the problem.
Character models are the most noticeable asset difference by far. Metro 2033's original wooden-faced people are swapped out for Last Light's set, and it's an enormous upgrade.
However, there are a ton of smaller changes too. Lighting is given a lot more room to stretch in 2033 Redux. The original 2033 was very bleak and built its indoor environments well, but everything was lit rather flat when compared to Last Light. I know—I didn't believe it either when I first started writing this review. Take a look at these screenshots though:
Metro 2033 
Metro 2033 Redux Side-by-side, there's no doubt that 2033 Redux has more dynamic lighting and a greater focus on contrast. By no means does 2033 look bad, but it has an oddly flat, bright look to it in retrospect that doesn't do justice to the dank subway setting.
There are also basic texture and geometry differences, of course:
Metro 2033 
Metro 2033 Redux It's all well-and-good, with a few exceptions. For some reason, 2033 Redux seems to massively cut back on particle effects, which were the most impressive part of the original. Many areas that used to feature snow or smoke now are empty, and I don't know why. For instance, notice the snow in the original's opening scene versus the bland, empty skyline in Redux:
Metro 2033 
Metro 2033 Redux Or the way light refracts off the snow in the original's doorway versus the flattened look of 2033 Redux here:
Metro 2033 
Metro 2033 Redux These are key examples I found within the first hour of the game, and they're a noticeable downgrade as far as I'm concerned.
And as I said, Last Light gets almost no visual bump at all. Here are screens from the two so you can see the similarities:
Metro: Last Light 
Metro: Last Light Redux The changes are minor at best, such as the way this sign is illuminated in Last Light Redux:
Metro: Last Light 
Metro: Last Light Redux As for Spartan and Survival Mode, the gas mask wipe, and the rest of the feature changes in 2033 and Last Light Redux, some are great and some are middling, but nothing felt objectively worse than the original versions.
I'm not sure Survival Mode really makes sense. Spartan Mode in 2033 is totally fine—you're given more ammo, (presumably) more health, and it generally makes the game a bit easier. I don't know many 2033 diehards (like myself) who will ever want to play 2033 Redux in Spartan Mode, but fans of Last Light who found 2033 punishingly difficult will appreciate the change I'm sure.
But Last Light in Survival Mode is just kind of clunky. The game was designed as a run-and-gun shooter, and just because you give me less ammo doesn't make it any less of a Michael Bay-esque affair. The complaints about Last Light were, as far as I'm aware, that it took the bleak and oppressive, under-staffed and under-equipped world of 2033 and turned it into a fast-paced, superhuman shooter. In other words, the Dead Space to Dead Space 2 predicament.
Metro: Last Light Redux None of that is fixed by giving me less ammo and making enemies more aware. The game is still paced like a crazy thrill ride, regardless of how many bullets I have, and nothing has been done to make Last Light's tone match 2033 more.
Don't get me wrong—I still enjoyed Last Light. It's a very different game from 2033, though, and not in a way that can be solved by Survival Mode. You'd need a complete overhaul of every level and a fundamental redesign of the game, neither of which was attempted here (for good reason).
As promised, 2033's levels get reworked a bit too. There are a few new encounters, though you'd be hard-pressed to point out which ones unless you've played 2033 very recently. A few of the inter-level loads have also been removed, which is great.
Metro 2033 Redux Metro 2033 Redux even gets swanky new load screens.
We could also talk load screens. There are new graphics on 2033's load screens to match Last Light's aesthetic, and the load music has been swapped out. In fact, I'm pretty sure music has been swapped out even in-game. I can't be certain, which is testament I guess to the quality of this Redux version. However, some of the music seemed more bombastic than I remembered. In my memory, 2033's music was very understated.
If you've never played Metro 2033 and Last Light, you're missing out on a fantastic series—probably one of my top five shooter experiences of last generation. The games are excellent at world-building, and where many games toss around the word "immersive" I think Metro is one of the few that can actually lay claim to that term. The Redux versions would be a great place to jump in if you missed these the first time around.
Metro 2033 Redux in Spartan Mode is great if you loved Last Light and never could get into the original—it's like an additional easier difficulty, meant for fans of shooters instead of stealth games.
For people who've already played and enjoyed both games, the Redux versions are a weirder sell. I personally think the Redux version of 2033 looks better (despite some missing particle effects), but I know some purists might not. You can't please everyone, but I'd say 2033 Redux is a great buy if you really love the original and want to replay a tuned-up version.
Last Light Redux, on the other hand, is basically just Last Light Game of the Year Edition. The changes are far more minor, and the inclusion of Survival Mode is unlikely to assuage the ill-feeling many 2033 fans had at the game's action-packed emphasis on set-pieces and bombast. It's more suitable for people who didn't just buy Last Light a year ago.
Got that? Newcomers, jump on in. People who haven't played 2033 but enjoyed Last Light, come on down. People who own both already, use your best judgment.
From PC World. Electronics product reviews and advice for best reference
Metro: Last Light $60.00 Metro: Last Light is a flawed game with genuine pathos, a unique first-person shooter that accomplishes more with its narrative than some films.Following in the footsteps of 2010’s Metro 2033, Metro: Last Light improves upon the gameplay of its predecessor without destroying what made the series great in the first place: the setting. Last Light takes you back to the post-apocalyptic Russian wasteland, employing an excellent soundtrack and bleak, desolate imagery to deliver a first-person shooter with surprising pathos and one of the most genuine game narratives in recent memory. Boot up Last Light and you'll be dropped into the boots of Artyom–a man haunted by memories of his mother, or lack thereof–as he attempts to leave the Russian Metro to capture “a dark one”, monstrous remnants of the world before it was devastated by all-out nuclear war. Of course, nothing goes smoothly for Artyom, and along the way you'll be captured by other survivors and work together with another captive, Pavel, to orchestrate an escape. Arytom's quest ranges across the Russian wasteland, ultimately leading you through areas devastated by nuclear destruction and nests of enemies mutated by the apocalypse before culminating in one of the coolest and most intense firefight finales I've ever experienced. 
In Last Light you'll leave the underground Metro to explore the desolate surface, and you'll need to carefully shield yourself from the fallout if you want to survive long up here. But frenetic, fast-paced combat is tiresome without a meaningful reason to fight, and Metro: Last Light tells a meaningful story through emotionally-charged flashbacks to the moment the nuclear missiles struck, and how that moment affected the Russian people. It’s a series of powerful scenes scattered throughout the 9-12 hour campaign that don’t force themselves on you, allowing different players to experience as much–or as little–of the narrative as they like. That’s one of Metro’s greatest strengths: it doesn’t force anything on the player. There’s plenty of optional areas to explore at your leisure, allowing you to intuitively control how long you spend in Metro: Last Light's bleak alternate reality. Moment to moment, the actions you're taking in Metro: Last Light are very similar to those you performed in Metro 2033: exploring, scrounging, and fighting for your life with a hodgepodge of unique and innovative post-apocalyptic weapons. Even your weapons tell a story, like the handmade submachine gun that has a magazine that slides left-to-right, through the weapon, as shots are fired. It’s a little thing, but idiosyncratic touches like this do an excellent job of showcasing the unique, alien nature of Metro's alternate reality Russia. Of course, those crazy cobbled-together weapons can be customized to fit your tactical preferences using Military-Grade ammunition, high-quality bullets manufactured before the apocalypse and now used in Metro as a form of currency. Paying a gunsmith to modify your armament with a silencer, lasersight, stock or foregrip is a simple way to significantly change the characteristics of each weapon, allowing you to tailor the game to your liking. 
The soldiers of Metro rely on an assortment of pre-apocalyptic firearms and improvised weaponry to defend their territory. Your limited inventory also forces you to make some meaningful tactical decisions: mod a semi-automatic pistol to be fully automatic and pair it with extended clips, for example, and you can use your new pistol to replace the submachine gun in your inventory. That in turn allows you to drop (or sell) the SMG, using the newly-opened space in your three-slot inventory for a long-range tool like the rifle. It's a seemingly small decision that could mean the difference between living and dying when you're exploring the wasteland on your own. Metro’s score is one of the best in the business and continues to establish not only the singular tone for any particular moment within the game, but a consistent and omnipresent theme throughout the entire narrative experience. Pair this with the spot-on sound effects–terrifying gunfire, wet gurgling screams, the frantic cries of communication between both enemies and the occasional comrade–and you’ll a sense of aural immersion to rival that of any great blockbuster war flick. The sound design remains exceptional throughout the game, tbough there’s a bit of weirdness with characters occasionally acting out of sync with their audio. 
Play Metro: Last Light on a powerful gaming PC with a good set of speakers if you can–you'll be amazed at how engrossing the bleak landscape and stirring soundtrack can be. Unfortunately, for as strong as Metro: Last Light is, it suffers from a myriad of bugs and issues that can often disrupt the atmosphere it works so hard to evoke. Crashes to the desktop and random minimization happen all too frequently, destroying any sense of pacing that you might have. Occasional hard locks and freezes join the list of serious technical problems, but by far the most frustrating bug I came across was the seemingly random times that the player would become immobile and unresponsive, regardless of whether I was using the keyboard or the gamepad. It usually happens when both the protagonist and an enemy–especially the mutated creatures–make a melee attack at the same time, causing Artyom to become unresponsive, almost as if stunned. Bugs aside, Metro: Last Light still isn’t for everyone. It suffers from a lack of direction that often left me backtracking and searching the same areas multiple times before figuring out what to do or where to go. Some may find this lack of guidance charming, but it feels like even the most simple of navigational suggestions are absent and the experience suffers for it. But the main challenge of Metro: Last Light isn't just poor directions–the game is hard. The two difficulty settings, Normal and Ranger (a special, harder difficulty setting that was made available as DLC to players who pre-ordered the game) are a perfect balance of what you want in a game like Metro. I can't speak to Ranger mode, but Normal is just hard enough that it forces you to slow down and think tactically in situations where, in other first-person shooters, you’d normally just run through guns blazing. That kind of recklessness will get you killed immediately in Last Light. Despite its technical flaws and poor guidance, Metro: Last Light is a uniquely challenging and heartfelt experience, a bleak first-person shooter that does more with its narrative that some films. It works well as an isolated experience too, making it a great entry point into the Metro series.