Donkey Kong Jungle Beat. Personally, it's one of my favorite games ever, across any system, and hardly anyone I talk to have even played it! I feel like this game was overlooked because of the bongo controller, but, it actually is a really in-depth platformer game, and one of the most underrated/overlooked games ever, IMO.
Challenge Mode scores: 230, 300, 249, 100, 299(perfect!) Overall: 1178 All the info is there, except the info that isn't there.
Gotcha Force Donkey Konga (1, 2 and 3 equally, although since 3 was JP-only that's more understandable) Chibi Robo The Legend of Zelda: Four Swords Adventures Animal Crossing (the series as a whole is well known but the GC version is largely forgotten) Pokemon Colosseum Pokemon XD Kirby Air Ride Pac-Man Vs. (Multiplayer-only and completely overlooked most of the time) Sonic Adventure 2 Battle (Chao garden mode is incredible)
There's also a good 10 or so Japanese games that I feel are very enjoyable but are overlooked due to region locking, which is very easy to bypass nowadays with a Freeloader.
The Legend of Zelda: Four Swords Adventures (people want something new in their Zelda games. They get this and no one wants it?) Wave Racer: Blue Storm/1080 Avalanche Dragon Drive: D-Master Shots (import) BOTH Bomberman games
-Incredible Hulk Ultimate Destruction (NOBODY talks about this awsome game.) -Star Wars Rogue Leader (I might be stretching it a little, but nobody seems to remember this ever existed.) -Pac-Man World 2 (I bet you never heard of it until now.) -SpongeBob Battle for Bikini Bottom (Yes, I think a SpongeBob game is good, sue me.) -Lego Star Wars 2 (Yes, I like a "baby" game, and more people should like this game more.) -Star Fox Assault (It's better than Adventures by a mile.)