WarioWare is one of the funnest, most addicting games I've played in a quite a long time. It's just a big grouping of mini games that you play by jumping, swaying, hoola-ing, squating and any number of other moves.
Each mini-game is a collection of 10-20 twitch movements (pick up the controller when the speaker rings, jump rope, flip a pancake) that unlocks another. Each game pretends to have a story line, and with that comes a funny intro cartoon. Those are actually usually longer than the actual game.
The graphics aren't the greatest in terms of realism or sharpness, but the Wii was never intended to tout stellar graphics. They're cartoony and fun and keep you hooked in the game.
The best part of WarioWare is that it's great to play with kids, and even more entertaining on a 'drinking night'. And since the games are so short, you don't have time to ger bored with them.