I hate Counter-Strike for its ridiculous gameplay. It really never should've been labelled realistic. At all. Ever. It simply sucks.
However, since you lumped it in with the brilliant single-player experience that is Half-Life 2, I had to vote for it. These games don't seem to have much in common; FSW is good too but it's a completely different type of game from HL2 (still not as good, though).
"Mankind, when left to themselves, are unfit for their own government." - George Washington