There's this NES game called Dick Tracy (based on the film), but anyway, when I got it I was too young to understand what to do with the game so I would just run around doing things that really didn't furhter the progress of the game. In 1999 I picked the game up again and managed to figure out what to do (find clues and persecute the criminals those clues point at). It came out in 1990 so it took me 9 years to finish it. But maybe that doesn't count.
I remeber one of the star oceans for PS2 maybe, being advertized as being the longest game ever.