I hate games like this one, if only because I can see the tons of potential being wasted.
If I was a game critic, I'd have to say that this game is pretty good for a rail-shooter. I'd say how it takes inspiration from Half-Life and how it's all fine and great. But fortunately I'm not a critic, so I can point out that the game sucks as an RPG. But unlike in Half-Life, this game, the setting in particular, doesn't lend itself to a linear rail-shooter very well.
In half-life, you always had a great illusion of freedom. Although it was obviously a linear experience, in no or few points did the player feel constrained or confined. The player merely did what came naturally, making the linearity mostly a moot point, as most players would have followed that one particular path anyway. Here, on the other hand, the illusion is crude and uneffective. Railroading in a subway tunnell is something I expect, but when I see that traversing a city is just as linear as the tunnell, I feel something is definitely wrong. Especially as the plot itself calls for exploration of some sort and the mechanics themselves involve money and trading. I won't be kidding myself saying I'd expect a full RPG - that would be ludicrous, but a tasteful hybrid like Stalker? Definitely.
While we're on the topic of Stalker - being an eastern game and, in fact, developed by some of the same people who previously worked on Stalker, a comparison is inevitable, even though I'm sure that's something the devs of metro would try to avoid. Metro 2033 is stalker's younger brother - nicely groomed and dare I say even metrosexual in his next-gen appearance (forgive the pun), but ultimately with jelly for brains and little real ambitions beyond looking hot. It doesn't just borrow from classic FPS titles like half-life, it blatantly rips off the ideas and pacing to the point of being a remake, all while missing certain subtle yet crucial points that distinguish gunk from a masterpiece.
Metro 2033 has a lot of great ideas but is ultimately brought down by an incompetence in implementation, lack of ambition or jarring inconsistencies. For example, the very first SMG in the game has a box magazine that allows you to see how many bullets are remaining. Each time you shoot you see the shells come out and the magazine move, seeing just how many rounds you have. Really great thing. But once you put the gun down, even if empty, it lies on the ground with it's magazine obviously full regardless if in reality it has any bullets at all. Gas masks are required to protect you from the hazardous environment and can get damaged, but quite often upon swaping the filter only the animation plays, while the game state doesn't registger the change. And thanks to the linear nature of the game and lack of planning, you rarely know where you're going next, and thus don't plan for what's ahead. In a real survival game this would mean death, but here the developers prevented that by gratuitously littering the hostile world with essential air filters, so that even on the hardest difficulty I didn't have to worry even once about running out of that resource. There's no point in adding a gas mask feature if the developers then make triple sure you'll never be able to humanely run out of resources, short of standing in the middle of a deadly pool of bubbling vitriol, turning off the monitor and going out for the night. Metro 2033 likes to build hopes and then deliver disappointment.
In summary, I can't say I recommend the game. The atmosphere is really great, the individual ingredients seem tasty, but the overall dish is palpable at best. It suffers greatly from a visible lack of ambition and seeing just how much potential was wasted is far more depressing than the already bleak and hopeless world the game is set in.