Yea, I too have found myself surprisingly in love with Wii Sports. I thought it would be a real nice "Hey guys, this is what the Wii can do" title, but not much more. However, its the title I have spent the most time with so far. Other games I got are:
Tony Hawk Downhill: Its okay, personally I expected this title to be a little better. I think its mostly due to the learning curve and that I have not spent much time with it so far, I'm sure once I really get it down it will be alot more fun (considering the reviews and my love for snowboarding games). One thing I discovered in my last few minutes of play is that its ALOT easier and more enjoyable to just use your right hand when steering, and grab on with your left when your doing tricks :-D
Trauma Center: Awesome game, really...really awesome. This is the game my mother purchased (shes a nurse, hasn't wanted anything video game related my whole life but actually made me sit with her in line for the Wii launch to make sure we had one ON Sunday, lol) and I decided I'd give it a go too. Man, I am having a blast with it :-D
Monkey Ball: This is my first Monkey-Ball experience, but with the 50 mini games I wanted to grab it (we got 4 controllers, I have a brother and a sister, a father and a mother, and my girlfriend stays with us half the week...enough around to play all the time). Well, I was disappointed with it at first, but only because of my lack of experience with the Wii-Mote. I had a really tough time controlling the game at first, but the more I get into it the more I like it. Now I have finished the first three worlds and am proficient enough to fly off and find some nice short-cuts :-D, having a real good time with it now. I'm sure if your a Monkey Ball fan you will love it, and some of the mini-games are alot of fun too (darts is great).
Just wanted to add, is anyone else eagerly waiting the first real feature-full boxing game for the Wii? I am loving the boxing on sports, but its not really as responsive as I would like - would be great to see a more detailed title released.