Funny to see the Wii leading the poll here, but this is a Nintendo site...
It's far easier to name a dozen quality titles from the PS3 or 360 library than it is from the Wii library. I give it to the 360 based on the game quality to price point ratio along with a far better online service (you get what you pay for...). Sony definitely had the console with the most potential but they squandered it all away with poor decisions and dev's weak utilization of the power available to them. Nintendo made their money off of a gimmick. I don't think motion controls themselves are a gimmick. It's the idea of foregoing any sort of technological leap to put out a console where motion control was the only thing it had going for it. Can you imagine what kinds of adventures Mario, Link, and Samus would have had if the Wii had any sort of power behind it?