Watching Banjo get played makes me want to go back and play it, I disagree with Jeff and think it looks like it holds up great. Like Conker there's just a lot of great art direction(especially in Tooie) and variety. They really open up a lot as you progress.
Edit: I feel like none of them ever got far enough in these games to realize how different the Banjo games were from Mario 64. The creature transformations, mini-games, vehicles, shooting elements, and so on. They're really interesting games! Sure you're collecting things as you go along, but you're doing a lot of a great puzzles and varied platforming along the way.