Probably this:
This:
This:
This:
This:
This:
This:
This:
etc, etc... I really don't know which my first game was... I was like 4 when I started gaming, lol.
EDIT: I just realized how old the famicom already was when I started playing it. I didn't even know I was behind the times :P I wonder where it is, I should still have it somewhere... or maybe I left it at my grandmother's house when I was young... and if I did then she probably doesn't have it anymore...