assuming you dont have a top of the line gaming comp, half life 2 and fear wouldnt be a good choice, niether would something like call of duty 2 or battlefield 2, these require pretty decent systems, and youd be cheaper buying an xbox or PS2 instead.

Starcraft is an oldie but goodie, command and conquer is the same type of game but with a more military feel, both are real time strategy where you are a commander and control hordes and hordes of troops tanks, etc. I havent played Civ 4 but heard its pretty good. There are a mound of games out there, maybe look at an EBgames store, or gamestop and see whats out, alot of the times you can get a preowned game.

A little more information on your computer and what your looking for would be better.