IDK, BF2 would be good but it is to me only because i got into a long time ago but for someone just getting into it now....
I voted FEAR. Cool graphics but the level repetition like mike said is pretty lame (and for me, i didnt even want to finish playing the game because i was so bored about half way through). LOL maybe it's not the best one to get now that I think about it.
I would have said HL2:ep1 but it's a pretty short game so maybe not the best for the first game to buy. But it is rather cheap too so maybe buy that one too? You won't be disappointed, it tells a pretty amazing story not to mention the gameplay is astounding!
Out of that list i would be interested in trying STALKER. It sounds and looks pretty cool (although a little buggy i hear but not so much that it makes the game completely unplayable or even that annoying).