We got a Nintendo when I was preschool and I tried and tried to beat any game on that system but always failed, they were too unforgiving for my age. When I was in Kindergarten I got a Sega Genesis and (using the up, down, left, right, a, b, select code) skipped to the final level and beat it.
As for the NES I honestly don't remember beating a game from it until around 2006 when I beat Super Mario Bros 3, before that, the closest I got was getting to the final 3 stages of Chip n' Dale Rescue Rangers and always running out of lives near the end.