I will GLADLY submit 2:
The Oregon Trail- I never made it to the other side to see the crappy ending; I either got bored and put the game on grueling pace (to see how fast my "family" would die), try to ford the Mississippi River, or hunt game until the winter months caught up to me (usually in the mountains). Then I would simply type the words "I hate this shitty game" into my tombstone so that other players who played it (remember: we had the old Commodore systems with FLOPPY DISKS) could be better prepared to go past my grave about 13 times.
Where in TIME/USA/WORLD is Carmen Sandiego: Whoa, talk about a waste of time---yeah, it taught you geography, people, and places, but did anybody out there actually CATCH Carmen in one of these games (until of course, she would lead the jailbreak just so the game had NO ENDING)?