Which do you think will be better, and why?

BOTH

Stalker: africa

and

Stalker clear sky.

Clear sky probably has the edge, because already have an idea of AI and Atmosphere im going to get.
The faction stuff sounds awesome.

Though far cry looks pretty sweet.

All the this involves at least some sort of computer upgrade i think.

I've never been the biggest Far Cry fan, but this new one looks amazing and I can't wait to play it. That being said, I would still have to say that Clear Sky gets the edge for me. It looks great and I really enjoyed the original despite it's issues.

Well, I'm getting both, hands down.  But if I had to guess which one will be better, then that goes to Clear Sky.  Far Cry looks like it's going to be huge beyond all reason, but generally the environments look far less detailed than Clear Sky and STALKER has a mood/atmosphere that's just so compelling.  Plus I've never thought of Ubisoft as being "over-ambitious" and GSC is nothing but over-the-top-shoot-ourselves-in-the-foot-and-delay-our-game-3-years-over-ambition.

far cry 2 for me

both

missing out on either is a mistake

I really wish that Stalker could get a console release so that more people would get a chance to play it. I feel like it's such and underrated game (the first one) and I would love for the game to be as successful as it can be...

I think Far Cry 2 will be better because I did not enjoy the RPG elements of Shadow of Chernobyl. It felt like I spent too much time away from combat, doing things like: talking to NPCs, traveling (which was made harder by a heavy load), searching for things...

stalker was fun but was kind of a broken game far cry looks way way better

Far Cry 2 will be fun. But it is trying to do alot more than the first FC, that we don`t really know how it will turn out. Stalker: Clear Sky is looking really awesome.

Missing out on either would be a huge mistake but if I could only have one it would be Stalker: Clear Sky.  Stalker isn't just a straight FPS game it has other elements as well as a good atmosphere.