Mario Galaxy 2 roughly 95% new content
During today's Nintendo roundtable, Nintendo legend Shigeru Miyamoto said that Super Mario Galaxy 2 was originally intended to be a remix of the original Galaxy's content. However, it was expanded into a full sequel.
A small percentage of the game -- about five percent -- is essentially composed of remixed levels from the first game. But really, only five percent? We'll live.
Game's out in 2010.
We'll keep you updated as Miyamoto continues his talk.