Wario has many new and returning combat moves and they are really satisfying to pull off. For example: He can pick up objects and enemies and spin them around, which is useful to defeat more enemies at the same time or open a door by spinning a wheel.
Each world has two levels, and one boss level. There are three objectives per world: collecting all the Wario Statue Parts, collecting all the Red Diamonds, and beating the boss.
If you collect all the treasures in a world, a microgame can be unlocked in WarioWare, Inc.: Mega Microgame$!, which can be played with a Game Boy Adapter.
The levels are huge.
Nice looking graphics, especially for GameCube.
Great Soundtrack, which fits Wario's style perfectly.
The plot where a Dark Jewel caused many of Wario's treasures to be turned alive and designed in a weird way is pretty original.
The fixed camera follows Wario, and makes the hardware able to render more objects on the screen without framerate losses.
You can rotate the camera in the puzzle areas, because they are small rooms, and there's not much to render.
If you get a Game Over, you can continue the game where you lost if you have enough money.
You can get Garlics to restore your health too, and they dont cost too much, making Game Over's a rare case.
The Manual is full of Wario like jokes, and they are actually kinda funny.
Multiple endings: The more spritelings you save, the bigger and better Wario's castle becomes at the end.
Some of the enemies and bosses may look out of place and creepy, though this is because of the Dark Jewel mentioned above.
If you fall into a pit, you fall into Unithorn's lair, and you need to find the box that has the escape spring to exit. It's a really irritating part of the game, because every other box has a bomb inside, and you can lose coins if a Unithorn bites Wario.