Mine are:

1.Command & Conquer:entire series is amazing supreme commander is cool too

2.Doom: the original FPS has evolved into a most addicting horror story

3.F.E.A.R.: like Doom is horror based, fun playing in the dark

4.Prey: One of the best graphic engines ever with fun storyline and weapons.

5. Quake 4 is only great single play but still cool

1.Command & Conquer:entire series is amazing supreme commander is cool too

2.Doom: the original FPS has evolved into a most addicting horror story

I like .........

Counter strike
COD
DOTA
Mostofa
Doom

I would say as
1) Age of Empires 2: Age of Kings
2) SimCity 2000
3)  StarCraft
4) Counter strike
5) NFS underground

F.E.A.R.: like Doom is horror based is my favorite.

I like:
3.F.E.A.R.: like Doom is horror based, fun playing in the dark

4.Prey: One of the best graphic engines ever with fun storyline and weapons.