A mix between the Generations Boost style, and The Lost World adventure style game play, would be a perfect game play for sonic in the main games.
Now these two styles of Sonic have been around for a while, they've just both been tweeked around with in recent years. Weather it be the boost gameplay going from a simple track course to have more twists and turns, more enemies, punishment for boosting willy nilly, and well.. just being fucking AWESOME! Then the lost world style which simply took the sonic adventure sonic control scheme and added to it. they make it so you have different attacks (bounce attack, op as hell spin dash, a sonic cd style kick, and a tweeked homing attack), you control your run speed with a run butten, have a more momentum based style like the genesis games, and finally the parkor based platforming which IRONICALY while sonic as a character has done many times, was only just NOW put in the games.
Both these styles of gameplay fit sonic really well, even if Lost world is slower then a normal sonic game. But that was only because of the mario galaxy type level design, they could EASILY speed it up. But the fanbase is split in between the styles, should sonic be built more like lost world minus the galaxy type levels, or should it remain the boosty type gameplay from Unleashed/Colors/and Generations? To that i say both.
Take the best of bothw orlds, and make THAT how Sonic plays. As a paltformer, being able to control your speed for precise platforming, makes PERFECT seance so it'd be all the better to slow down if you want, as well as the parkor allowing for creative ways of platforming, wether it be wall running or pole flipping it all works. But in the end it is a sonic game, you should have to EARN going at top speed with out much stopping you. If you get careless you screw up, and even if you boost you'll smack into a wall or a hazard, or even a death pit. But at the end of the day you'll be going fast. Combine all of this, you'll pretty much have sonic's abilities fully realized in game form.
It'd basically be the sonic cd intro but with modern sonic XD
but yeah, felt like writing this journal because i felt like it. It crossed my mind so i decided to do it, and truth be told i HOPE that's what sega is doing.. along with making the other characters playable since it'd allow for EVEN MORE gameplay awesomness.
OH but one last thing
... if the main games dont get new writers IM OUT. Seriously, in colors and generations i could tolerate them, but my god lost world was just.. wow..dissapointing. Not to mention int he handheld sonic boom game they did the exact same thing.. coupled with the fact the sonic boom games suck doesnt help either. so yeah.. one major thing to note there.