And they've already shuffled their leadership anyway, so they are taking Sonic in a fresh new direction for better or for worse as a result of pretty much the exact same thing you suggested they need.
Saying that Sega and Nintendo don't have any means of fanservice seems more the complaint of an angry gamer than the criticism of an observer. Shadow the Hedgehog was fanservice, Sonic Chronicles and Black Knight are so full of fanservice amidst the extras and promotions that in some cases it tends to outshine the gameplay itself.
Nintendo on the other hand often makes a significant effort to reward the veteran player's nostalgia (they still use Epona's song... for a good reason, and many Ocarina of Time situations are mirrored such as the Poe sisters, the freezing of Zora's domain, etc) and have been letting a huge amount of titles, some big name, some obscure, and some cheap trickle through the Virtual Console. Even if it is too slow for some disgruntled fans (many of whom probably already have the game pirated anyway), they are still offering classics to those that want to revisit them and those that have yet to experience them.
Another issue with Nintendo is that they are trying to service both their long-time fans and their new fans at once, which is never easy. The kind of thing the new fans want is easily produced, but the type of thing cherished by the veteran gamers (I refuse to use the terms hardcore or casual in this argument) takes far longer to make good on.
And I think that Sega itself is striving for a kind of fanservice previously unheard of on the Wii, by trying to deliver something brutal and yet innovative to make up for the lack of similar products in the gaming library.
Now, I for one think both Sonic Team and Nintendo are on the right track, give or take a few flaws. Sonic Team already hit bottom, even if Sonic becomes a different franchise than the one most of us grew up with, it is seeing improvements that make the game more solid. Nintendo is opening gaming to a huge unexplored userbase, and trying not to sacrifice their old userbase. Its not easy, but they've done a decent job so far... I don't think I could so easily try to live up to the expectations of such a reputation as theirs and simultaneously deliver on the new demographic. (and to use Twilight Princess as an example again, wherever it was easier than its predecessor was more the result of removing some cheap aspects of the old game than dumbing down the new game)
