I played the original Metro 2033 when it came out. A GPU I bought came with a free Steam key. I enjoyed Metro 2033, but I have mixed feelings on Last Light. Both rely on auto saves at checkpoints, and does anyone like this? I had heard the redux versions had some bugs, and they do.
The only complaint I had with the original Metro 2033 is that a short press of the reload button does a regular reload, and a slightly longer press of the reload key loads military grade rounds (MGR). In the Metro games MGR is the currency, but you can also use it in your gun. It's more powerful, but it's rare and literally burning money. In the original Metro 2033, I accidentally loaded my MGR and didn't realize until I got to the next station and found out I didn't have any money. I was careful this time, but still managed to do it a couple of times, but luckily I realized it before I used too much of it. I really wish they would have added separate reload keys for regular and MGR, because it's too easy to switch by accident.
I played Last Light Redux for Halloween and didn't enjoy it as much as 2033. It was part bugs, and part bad game design. There is an extremely buggy section (Bandits) where your auto save is pretty much guaranteed to become corrupt. It's also a roll of the dice if this mission breaks your ability to do stealth take downs, and if it does you have to restart before the mission and hope it doesn't break because it will persist for the rest of the game. I had to re-play it 3 times thanks to auto save corruption. The first time, I simply quit part way through the mission to eat and it crashed loading my save when I came back to it. I had to restart the chapter, then the AI bugged out and became unresponsive, unkillable statues, and again corrupted the auto save. The third time, every time I saw the game auto save, I would ALT-TAB out and make a backup. That way I had more than one auto save to try if the current one corrupted, but luckily I didn't need it. I also got lucky and didn't experience the stealth bug.
For some odd reason in the Redux version, you can't buy air filters from the stations (maybe just on the harder difficulty) and have to scavenge them. That made surface missions extremely frustrating. I played on Ranger Hardcore, and I was finding the game easy, then around mid-way through, the game decides to troll you. You're on one of the surface levels, which itself was fine, but then they throw in a boss fight right at the end when you have no air and no ammo left. My first try, I had less than 2 minutes of air and 17 bullets. I had to re-play it several times, and I almost quit the game because of this level. I basically had to remember where the supply drops were, avoid enemies, and use a bit of a "cheat" where you take off your mask, wait until you're about to die from lack of air, put it on, take a breath and take it off again. I started with 9 minutes of air, and even doing the mask "cheat" and picking up air filters along the way, I still get to the boss with ~3 minutes of air. I also had enough ammo to take down the boss with a little bit of air left. The previous and following levels were pretty generous with air filters, but not this one.