I think the recent losses are due to the Wii reaching the end of it's life, and the 3DS looking like nothing more than a minor upgrade for the DS.
Mario is not to blame. Although they do rehash the games every few years, I would argue that Nintendo are not alone in this.
To prove this point I give you some non-scientific, anecdotal evidence that may or may not be representative of the current situation for everyone else: on my X Box, I'm currently playing Skyrim, MW3 and Dirt 3. I sometimes revisit Fallout: New Vegas, NFS: Hot Pursuit, and Street Fighter 4.
All of those games are sequels and/or rehashes. (I could go on, but those are my favourites at the moment, and I have no reason to bore everyone with the rest of my collection).
On the other hand, I would argue that Nintendo have innovated over the last 5 years or so. They have bought games to markets that did not accept/care about games before. They have taken a completely different path to MS and Sony in this generation, and it worked for them... but all good things come to an end and Nintendo no "something else", and *that* is the cause Nintendo's problems right now. If they can innovate again in the next generation, then their current problems are temporary.
