I grew up on M.U.L.E., Ultima III and Racing Destruction Set on the Commodore 64. Here are some of the games I've played, I'm playing, and I will be playing (hopefully) some day.

Classic games
Chipwits (Mac 128 K)
M.U.L.E. (C64 & Atari)
Railroad Tycoon (Mac version only)
Vette! (Mac version only)
Lords of Conquest (C64)
Robot Odyssee (Apple II) [click here to download a 200 Kb binary + Apple II emulator for windows]
PC games
Ultima 1-6, Ultima Underworld 1 & 2
XCOM: UFO defense
System Shock
Magic Carpet
Warcraft II
Command & Conquer / Red Alert
Total Annihilation
Heroes of Might & Magic II
Dungeon Keeper
Good games I should get one of these days
Archimedian Dynasty
Battlezone (1998 version)
Close Combat: A Bridge Too Far
Dungeon Keeper II
Giants: Kabuto
Flight Unlimited II
Jagged Alliance 2
Myth: The Fallen Lords
Railroad Tycoon II
Realms of the Haunting
Seven Kingdoms
SimCity 3000