Best STALKER game?

Chernobyl, then Pripyat but Pripyat is better.

Avoid Clear Skies.

Hmm, either Shadow of Chernobyl or Call of Pripyat..

I'd say, go for Pripyat first, and if you liked it, get Chernobyl at some other time.

clear sky after patching

Chernobyl with some good mod.