Never would have predicted this. Seemed like an April Fools joke when first announced, looked lame (come on, it's just Track and Field and Olympics events with Nintendo characters! Nevermind that Camelot can turn any sport into gold by throwing Mario into it... this is the Olympics we're talking about!). If there was any doubt before that Mario and Sonic have finally stopped being bitter rivals (in that they can stand to be next to eachother now), I think that's all gone now. I'm reduced to saying: good job for making the game popular, I'll never play it but I'll never say bad things about it either.
...whoa, did Europe never get Mario Golf or Mario Tennis? Shoot! Those were great games. Let's hope you'll see them on Virtual Console.