Even though it looks like crap and from what you say, it sounds like crap... I still want to give that game a try. I'm a huge Mario fanboy, so even when it comes to strange spin-offs such as Super Princess Peach, I'll still want it.
But anyway, the worst game I've ever played... DDR: Hottest...
I haven't bought any games that were bad or embarrassing. But if I had to choose which one was the most annoying/difficult, it would be Izuna: Legend of the Unemployed Ninja. I got it about this time last year, and still haven't beaten it. Then it got corrupted when I came close. But I still...