Sonic Generations was in development for Wii at one point, don't hope for Mario/Sonic adventure game

A portion of a Nintendo Power interview with SEGA’s Takashi Iizuka…

NP: Given the success of Sonic Colors, why isn’t Sonic Generations coming to Wii?

TI: The primary goal for the console versions of Generations was re-imagining the series’ classic zones in vivid, high-definition graphics. The Wii hardware wasn’t a good fit for that concept, so we abandoned development on that, and decided that for our Nintendo audience, we would make a fresh start with a N3DS version of Generations.

NP: Mario and Sonic at the Olympic Games has been a huge success and another installment is due later this year. Obviously, many fans of those two beloved mascots would also love to see them team up for an action-platformer. Is that something you’d like to see as well?

TI: It took a huge event like the Olympics to make it possible to bring Mario and Sonic together. While I’m personally interested in bringing various characters together for a crossover game outside of the framework of a sporting event, I don’t think we’ll be seeing Mario and Sonic costarring in a game outside of the Olympics.

Nintendo Power