To me Super Mario Galaxy and Super Mario Galaxy 2 are the absolute best Mario games of all time. The original game is better than the sequal though. I would love to see a third instalment in the series. However, I believe we will just see a spiritual sequal, borrowing parts of the game play mechanics from the Galaxy series, but with a new title attached to it. What name you might ask?
SUPER MARIO U-NIVERSE!! :)
Expect a release sometime in Q3 or Q4 2015...hehe