HL2 seems to have a certain "grit" look to it. I think its mainly in the textures and the way they use lighting. The Unreal 3.0 engine does a great job at looking real, without the plastic gloss that Far Cry has. I can't wait for the games using it.
Also, the only thing I like in these Far Cry screens is the HDR lighting which HL2 will be using also.