I've owned a Wii since January and have purchased 10 Wii titles thus far. This is the order I'd rank what I've played:
1) Wii Sports - best example of what the console can do, easy to pick-up and play whenever you've got a few minutes to spare.
2) Twilight Princess - IMHO the best Zelda title ever, even over Ocarina. The scale of the game, the score, the overwhelming number of things to do ... it's incredible. More linear than prior Zelda titles with a lot of Point A to Point B follow the prompt exploring, especially in the first couple hours of the game, but also with a darker theme and incredible cinematics (I'd encourage you watch both demos at boot up; the second is phenomenal, especially with the orchestration). Bosses are too easy, but each ones' introduction is a real treat! I think you really need to put about 10+ hours on the game to appreciate what you're playing; TP will not provide instant gratification.
3) SSX Blur - Combines the best of the first three, original SSX releases from the PS2, ignores the RPG aspects of the awful SSX On Tour. Probably the second best title in the franchise behind SSX 3. Controls take some time, and prepare to spend an hour on the tutorial practicing drawing uber-tricks before you figure out how to ever pull one off in the game. My impression is that Blur is more popular with people who skipped the SSX series on the PS2 (if that's even possible). Fans of the series who have played through all the prior games in the franchise will probably feel like smashing their heads in with the Wiimote rather than play Blur, because the Wii controls are just too radical a departure after building up 7 years of twitch muscle memory on the SSX franchise.
4) Excite Truck - Simple, mindless racer, but fun. Much like the NES 80s classic Excitebike, it's all about the angle of take-offs & landings and managing your Turbo without overheating. Slight learning curve on the controls, but a solid racer with many, many tracks to unlock. A must buy if you've got children.
5) Rayman Raving Rabbids - Entertaining, funny, but somewhat short. Great party game if you've got the cash for the extra remotes and nunchuks. The mini-games are usually more good than bad, and a few are gems that you'll replay over and over again. The 'cow tossing' and 'red-light, green-light' minis are fantastic.
6) Super Paper Mario - Solid, but ridiculously over-wordy with some dumb characters/dialog. Incredibly frustrating to have brought it home eager for some Mario platforming goodness, only to sit there pressing the A button for 25 minutes to skip the mandatory introductory dialog, then have to do that AGAIN for each family member in the home to access their own save slot. Excessive text makes this game virtually unplayable for the young ones. Both great and frustrating at the same time, I'd suggest playing before buying. If you just want mindless platforming, download Super Mario World from the VC instead.
7) Tiger Woods 07 - EA's classic golf game with motion controls added ... poorly. Has the most absurd character editor ever for career mode, which will suck up ten hours of your life and still result in an avatar that looks absolutely nothing like yourself. Workable if you figure out the swing mechanics, but an obvious rushed, first effort by EA for the Wii. (I am so darn sick of Hot Shots and Tiger Woods. Please. Please. Please could I just get a copy of the original Swing Away from the PS2 with the control scheme from Wii Sports' golf added? That's it. That's all I want.)
8) Madden NFL 07 - Best edition of Madden for any of the consoles this past year thanks to the intuitive motion control passing system. Though much of the greatness of this title is overshadowed by the motion control command required to perform a user-tackle, which leaves you in a really bad position if you screw it up, usually resulting in LONG TD plays for the CPU or your opponent.
9) WarioWare: Smooth Moves - Overrated. Short. "Beat" the game and unlocked everything in one sitting. Will be a solid title when it's a Player's Choice $19.99 bargain, but this game is not worth $49.99. Has no replay value for solo play unless you're seven years old, and as a party game pales in comparison to Rayman, Mario Party 8, and even Wii Sports.
10) Wii Play - Comes with a controller, so the game itself is effectively $10. The nine mini-games included are not worth ~$1 per game, though, unless you have children or a fondness for the classic game 'Combat' from the days of the Atari 2600. If that's the case, you'll probably at least enjoy the included tank game.
Several of my friends own Wiis, and they have raved about both Sonic and Trauma Center. I have not played either game, but I have heard nothing but great things about them.
