Kill the spin-offs, but let them make the platformers. When you give Mario a sense of "drama" (well... as dramatic as an E rated cartoon gets) and let it combine with the natural hilarity of an Italian Plumber Hero, it can make a pretty entertaining, if simplistic game. Especially when his movement and the power-ups are as polished as they normally are. Whether it's because Nintendo has been in the game a long time or because they set higher standards for their flagship, no character is as easy to control as Mario. He can't match the fluidity of the Prince, or the visual "cool factor" of Dante, but he always seems to end up exactly where you intended.
Also, if anyone tells Nintendo to make less DK games? I hope you fall of a cliff and land in a barrel cannon. I hated Jungle Climber and Barrel Blast, sure, but if they give me a genuine sequel to DK64, it might help me forget what Rare is doing to Banjo right now.