That's a very open question, and it will boil down to personal taste.
The concept of the game is pretty good, the story is different. The biggest appeal and draw to the game is that it isn't exactly linear, like most games. Which means you can go back and forth to the different levels all you want. It doesn't change 100% but each visit to a level might have more enemy AI or mutants there then the last. You can also go on side missions, which will have you running back and forth to the different levels.
Or you can play this game like a normal shooter and just meet the objectives and move on to the next level and skip the free roaming ability.
I didn't personally have any of major bugs with the game. But there are plenty of small bugs that makes the game annoying. The AI isn't as smart as one would like and sone of the NPC repeat themselves over and over until you want to kill them. On the downside there are a number of people who have different show stopping bugs, who can't proceed through a level and there is a bug where it crashes whenever they try to do a quicksave or Quickload. Not overly common, but still a concern
The game is a slow start, but ends on a fairly high note, where it's becomes a little more run and gun. It's got a good atmosphere to it and has a certain addicting quality about it.
I give it a 6 out of 10, as the little bugs started adding up and spoiled some of the fun with the game. The Multiplayer is a joke. The graphics aren't bad, but not cutting edge, unless you load a mod called Float32, but it's not without little bugs either. I have a X1900XTX and it can play the game well enough on max settings, but it can chew up some ram, especially under Vista, which can consume uo to 2GB while playing
They have a new patch (1.004) coming out and it's got a fair number of bug fixes, and in a few more months, they announced the 1.1patch, which will offer a pure free roam no story plot mode, with more of the A-life system. That's probably the most promising aspect of the game long term.
I also give it a buyer beware. The game may work perfect for you, or you may get stuck with a can't go any farther bug, at least until the 1.004 patch is released.
There are others over in the GSC forums, that state this is the best game they have ever played. I've played it more than I expected I would have, but right now there is nothing else out that I like.
You have to try it mate, there are a couple of new commands for your ghosts such as telling them to go weapons silent (Recon) or creep 'n' kill (Ghost Recon) and now you can save at any point by hitting the 'k' key and there are a couple of new team members that you can use although still only three ghosts are on mission with you, the only thing I don't like is your team keep asking what's going on if you leave them in one spot for too long but it's such a minor annoyance it does not detract from the fun of making headshots from 200 meters out.
Now they are making a prequel to S.T.A.L.K.E.R with DirectX 10 graphics.
There is some grayness around that. Clear Sky may or may not have DX10 support. GSC said it was a goal, but couldn't guarantee it would make it, at least in 1 E3 interview, but now it's listed as a bullet item. So it sounds like, they re committing to it
Why on earth are people comparing those two games?
If you are a true pure PC Gamer, you play games across all the spectrums or at least across all of the FPS spectrums. Is STLALKER the best game out ? If you played GRAW2, HL2, STALKER, Counter-strike and Call of Juarez, you would be tempted to say that you enjoyed GRAW2 better than the others. Some might say they loved CoJ better.
If the question was, Is STALKER the best First Person Shooter with a RPG element, then it would be a really easy question to answer.
Now if someone would have said, "no Command and Conquer 3 is better", then it would be fair to wonder why you're comparing the two.