My parents used to have an old hand-me-down Macintosh when I was in elementary school (~13 yrs ago) with a few games on floppy disks (the actually-floppy 5.25 inch kind). I might have the games lying around the basement if they weren't thrown out years ago.
Other than that, my first console was the Sega Genesis (Model 2, and I think the N64 may have actually already been released at the time), so I'd say Sonic 1. However, my older cousins had an NES, which they gave to me around the same time I got my Genesis, so Mario Bros, Excitebike, or (groan) Fester's Quest could be around here somewhere.