Definitely buy the N64 version.
Though I disagree that Super Paper Mario is bad. Maybe you didn't like it but you must see that it is a quality game and is full of original ideas. It's not not the same type of game as the GCN and N64 versions. SPM is a platformer with the style of a Paper Mario game so it feels weird to compare them they way you did (did that sound mean?). It also got high ratings if you check those before buying a game.