Deca Sports has a few general problems, and a few sports in particular stand out in this list. Controls generally feel slippery and delayed. In particular, this is bad in the Kart Racing game. It feels like the track is turning around you rather than your cart turning on the track. And cornering feels so tricky with the tilting of the Wii-mote, that I just wanted to forget about this game and never have to come back to it. Supercross is very similar to Kart Racing for these problems.
Badminton probably shows off the control delay more than the other games. It feels like there's a disconnect between your swing and the character's action. Of course, you can learn to anticpate and adjust your timing, but that's a lot less enjoyable than just being able to pick up the game and play. Badminton also has some of the most complicated controls in the game, and it doesn't help that control instructions are tucked away under a menu. Figure Skating was another game with a complicated control scheme. Of course, it can be mastered with practice, but try getting your non-gaming parents to pick up "moving the character with the analog stick and flicking up with the Wii-mote when you are in the center of the large circles." Wii Sports, this is not.
Not everything was as bad as that, of course. I found Archery to be one of my favorite games, and it made good use of motion controls to get you into the experience. Curling, as mentioned before, gets around the control problems by giving you time to set up your shot. The only thing you have to worry about after throwing a stone (shooting) is sweeping, which only requires you to remember how to shake the Wii-mote. Basketball was also pretty intuitive, and could get pretty exciting when the ball gets shifted back and forth between teams.
Again, something is missing here to make this a great game. The controls needed to be more responsive in the more active sports. The game is also missing charm, despite the cute and cartoony character design. It's worth a rental, but it probably won't see much play beyond a weekend.