Just 10 ?
In no particular order of importance:
The Alien Breed Series (amiga)
Turrican series (amiga ones anyways)
UFO enemy unknown / XCOM ufo defense
Steel Panthers (the remakes from Shrapnel games in particular)
Unreal Tournament (especially the first one)
Doom
Civilization 1 and 2 (as well as freeciv)
Baldurs Gate
Battle for Wesnoth
Metal Gear Solid (2 in particular)
Silent Hill (2 in particular)
Those are ones that stick out, but there's so many great games.
