My favourite game from the Nintedno 64 is Paper Mario (which i'm currently playing) or Diddy Kong Racing. I love those two games. But you can't forget the first 3 Mario Parties.
My favorite game, well series, is Banjo-Kazooie and Banjo-Tooie. They are really challenging and they have a lot of objectives to do. I also like the sense of humor they add to the games.