While this may be a bit overused, I want to talk about the most interesting thing that Sonic Team can whip at. That is: Karma Meter.
Within the most recent editions of games such as inFAMOUS, Epic Mickey, Spiderman: Web of Shadows, and Fallout, is that rather than seeing somebody make their own choices; you get to be the one that makes the decision.
Some of you guys have expressed your "dislike" of a certain character, sometimes you even hate the character in general. Now, with Morality, you could remove that specific character.
Performing certain actions, such as ratting someone out or killing a character, could possibly turn some of those allies into enemies and some of those enemies into allies depending on your choices.
Or, let's get deeper, Eggman puts Sonic in a Cole MacGrath situation and decides to have him "make a choice" between saving his friends and the one he cares about. Though, in reality, you were to make a choice?
Seriously, I think I'm on to somethin...
With a Karma Meter, Sonic could be what the player chooses to be: You could either be the hero or the villain (or Anti-hero).
This could even lead to... *drum roll* alternate endings.
Shadow the Hedgehog may have "attempted" all this but the game did not go through to the fullest extent, certainly not as far as other games with this concept.
This is something to truely think about in a future Sonic game and, who knows, this may happen in the future. It's bound to happen.