I would agree with several others that as far as "games" go, We Ski is the best implementation of the board. Wii Fit uses the board very well for what it is, and you pretty much get it anyway with the board. I played Ski And Shoot quite a bit last week and it's the next closest thing to We Ski, plus it has target shooting and a little strategy involved in keeping your energy balanced with your speed. Unfortunately, it's cross-country skiing and everyone knows that cross-country skiing sucks. It is actually kind of fun though, and pumping your arms to move your "poles" is actually a little bit of a workout.
Beyond that, the Tetris Party balance board game is little more than a novelty. The Balance Board controls in Skate It are so finicky they are basically impossible to use reasonably. The board controls for Shaun White Snowboarding are more refined, but the game gives you very little direction. The game ends up being more of a "I wonder what happens if I contort my body this way" experience than an actual game. Honestly, as a skiier/snowboarder for a couple of decades, I find SSX Blur to be a much more representative experience than most of these, but We Ski does a pretty good job. Rayman Raving Rabbids: TV Party is fine, but you really don't need the board to play and it doesn't add all that much to the game.
I have Jillian Michaels' Fitness Ultimatum but can't bring myself to play it after looking at screenshots and reading reviews.
One game that has not been mentioned that is actually my favorite of the recent releases is Skate City Heroes. Most people probably ignored it because it has a hideous cover and looks like the worst possible budget game, but the controls are well done. They are much less sensitive than the other two "board" games and translate well to the on-screen actions without requiring additional awkward actions. It's not the best game in the world, but I would recommend it over Shaun White and Skate It.