Hard Truck 2 (the best trucker I've had, that soundtrack...)
NFS Undergrounds and the first MW.
X3 Terran Conflict I loved, think it's like '07 or smth, but it will eat every single Hz of your cpu grunt. With enough fabs I've seen even 3770K struggle to play it at anything more than 10 fps, probably has to do with game being single-threaded and all.
X3 Reunion is a more boring version of TC, I just couldn't be bothered to browse every single station's BBS for missions.
Half Life 2
Quake 3
Age of Empires are nice, all 3 of them.
Runescape (put 5 years into it, still logging in from time to time)
There was some isometric game about shooting aliens in a base, similar to Alien Impact, but I just can't remember the name, played it like 10 years ago.
Starcraft: Brood War (old but gold)
my gf just reminded Sims, they're pretty old