Fallout/2
Starfleet 2 on Mega Drive (I think it was on Amiga etc too), mining could get tedious but so fun and engaging.
Star Trek Birth of the Federation - fun on 2 player, can be very difficult to impossible on some settings.
Phantasy Star 2
Striker 96 - best footy game on PS1, although it was released very early so was OOP by the time all the drooling fanboys bought a PS1 and raved about Pro Evo
X:Com Enemy Unknown - you simply must own this game
Columns - the ignored cousin of Tetris