XSp.

Dunno if I can call it my favorite one, but the NES TMNT at least has a special place in my heart (awwww)…

Maybe because I was mostly into RPG games in the Nintendo era, but still, Teenage Mutant Ninja Turtles was one of those great Nintendo games everybody knew and had played.
And it also spawned several other sucessful games on the same franchise… at least ‘till SNES.
Oh, and did I mention how freaking hard it was? You’d get all lost on that city map repeating the same levels over and over again.
Still, awesome!
Source: NESguide