Wii Sports: a source of cancer
Super Mario Sunshine: just a bad idea to start, and lame gameplay
Superman 64: superheroes shouldn't be so hard to play
Street Fighter 2: genesis version was better, and arcade was king
Gyromancer: naw man, naw
heck, the entire power glove made any nintendo game into utter crap. Rob the robot? Like two games, and they are much easier if you do it with the regular controllers.
oh yeah, new super mario brothers wii... this is a co-op rage game. Not since battletoads has there been a co-op mode where you spend most of the game killing eachother.
There are definately alot of really bad nintendo games out there. RPG fans actually have really only the DS for a nintendo platform (and handheld rpgs were always a bad idea). For the most part, most of the games come out with a bunch of meh instead of awesome. The real hype behind Star Wars: the force unleashed was that the wii would obviously get the best version, when the truth was just the opposite. The game was okay (not good, but playable), but the wii version was the worst of the releases in all departments.
Even the first party titles from nintendo have 'meh' releases. Zelda: the wind walker was extremely mediocre compared to the rest of the zelda games. Mario sunshine is sandwiched between 64 and galaxy, both awesome games, making it the ugly inferior mario game.
You can say that for any company. There is no series out there that doesn't have a weak link. Trying to name off 5 nintendo games as the worst will get you answers based off how it is compared to other games in the genre, frustrating difficulty and some fanboys. If you really want to see some bad games, look back to the NES era, when games needed the official nintendo seal of approval and controls were sinfully bad. Play some Silver surfer or Festers Quest. Play some castlevania 2 and enjoy the invisible pitfalls. Some of us put up with those games, but many gave up and burned them. The true sign of a bad game is when you refuse to even sell it or keep it, so you destroy it to rid the world of such horror.