wow, no love for starcraft? seriously, its easily the best rts ever made.
deus ex: best game ever fucking made.
but to be (kind of) orginal, you gotta play the orginal command and conquer: red alert and red alert 2 (3 is good but nowhere near as good as the first 2, obviously because ea made THE DUMBEST mistake when they closed down westwood). you can download the game for free (legally) on the internet and unless your computer is 20 years old you can run it.
other than that, super metriod, the orginal mega man and mega man x games, and definitly try the mm legends games (so im a mega man fan, wanna fight about it?). arc the lad, the first 2 star ocean games, suikoden 1 and 2, perfect dark, skies of arcadia, metroid prime, god i could go on forever here.