I've purchased a few games all at once:
Super Mario Bros 2 (NES)
Blades of Steel (NES)
Star Wars Episode 1 Racer (N64)
Army Men: Sarge's Hero (N64)
Tomb Raider: Legend (GC)
Batman: Arkham Asylum (PS3)
The thing is, I haven't started a new game on all of them. I'll get around to it at some point.
I don't know if it will count but I did purchase the two DLCs for Resident Evil 5: Lost in Nightmares and Desperate Escape.
My next purchase, though, is probably going to be either Assassin's Creed: Brotherhood or Skyward Sword.