Rayman is great, and makes great use of the Wii controller. Yes most of the mulitplayer games you have to take it turn, but I like this, as it gives you time for a breather, plus you get to watch your mates make tits of themselves (milking a cow).
Madden 07 is also great, I've played the 360 version and the Wii one and would definitely choose the Wii version. There's a really good multiplayer mode too, you can do street rules, 2 v 2 is a right blast, and once again the remote really does shine.
Wii play is a good laugh, but I think I'm still to play it one player. If you need an extra remote, I'd pay the little more to get it, as some of the mini-games do make for a nice change. Just don't go in expecting an in depth experience. None of the games are more than 2 player (a lot of them could easily have been more) plus you can't change any options like handicap or time.
Super Monkey is good too, however i haven't played it as much as I thought I would (played rayman more). It is very good though. Not all of the 50 mini games are good, but some are truly outstanding. The remote does work well with it, however it feels like you are more in control of the environment than the actual ball.
Now for Red Steel then. It's not as bad as a lot of people say. Some moments I really like, the next I'm swearing like I'm in Goodfellas at just how annoying it is. The control is not perfect and this is truly shown when compared directly to Call Of Duty 3. When playing Red Steel you realise it just takes too long to turn around and that's my main problem with it. I think first person shooters have still yet to find their feet on the Wii and Metroid will hopefully be the first one of many that properly work.
At the moment I'd probably go with Rayman. Great lot of minigames that will have you realise just how many directions (literally) the Wii remote can head in the years to come. Madden and Super Monkey are also worthwhile additions, as is Wii Play if you're going to pick up an extra remote anyway.