action/adventure with some fun, eh? A couple people here have suggested Zack & Wiki and honestly, you can't go wrong with the game. I've had it now for a couple months, unfortunately haven't found the time to play through the whole adventure, but I can tell you that the game is fantastic and you'll definitely enjoy it if your a fan of Nintendo games and more specifically, the Zelda franchise. The game feels fresh and polished, the frame-rate slows at times, but the game is filled with awesome puzzles that make amazing use of the Wiimote, possibly the best use yet. The levels are challenging, fun and memorable and the game has some nice extras and some pretty solid replayability, if you enjoy getting high scores.
If you're not into that, Resident Evil 4 is a masterpiece. One of my favourite games of all time. Originally for Gamecube (the Wii version is a direct port with Wiimote function and PS2 bonus stuff), it still manages to feel like an epic, beautiful...almost perfect game - and it is. I've beat this game 5 times since its release on the Cube and it has so much replay value its ridiculous, you're going to want to beat it over and over. The Wii features work nicely and the game still remains a masterpiece, even will all the fancy stuff you see nowadays.
You'll have fun with either one of those...at least I know I did. You don't got that long to wait for Brawl, but RE4 or Zack & Wiki will make a nice addition to your collection of games and offer adventures that you can keep coming back to!
Peace (I'd like to hear some feedback if you decide to purchase any of those titles [or rent them or whatever...] good luck!)
(edit) * Endless Ocean is an adventure game, but you won't find any action. I have yet to play it, but I know that it is an exploration game that simulates underwater exploration - it's more for a chill/relaxed artsy experience, don't think it's what you're looking for