Super Mario 3, or Super Mario World them two are closed to tied, with world maybe holding a bit of a nistalga factor as it was the single most impressive jump in techonolagy that i remember, going from 8 bit nes graphics to SNES graphics blew my little mind away. (I was faily young, under 10 or so at the time.) The jump from SNES to Playstation wasn't as awsome, i'm not sure why, mabye cause i was older. *shrug*.
With 64 being a close 3rd under them two.