Sonic Heroes was only good in the fact that it kept almost forgotten Sonic characters such as Vector, Espio, Charmy Bee and Metal Sonic alive. Espio was one of my favourites Sonic additions, of which there are plenty to choose from. Sure the gameplay in Knuckles Choatix got frustruting as hell at points but it was still some mindless Sonic fun.
Sonic '06? Never played it, don't ever want to. Playing any Sonic game which is rated far worse than Sonic Heroes, SA2 and Shadow the Hedgehog might actually make me cry. The graphics didn't look too bad from videos I've seen but I think it was universally agreed that it wasn't that element of the game which made it so terrible, more the constant bugs.
My dream for the next Sonic game is a 2D game with pseudo-3D graphics that plays like Sonic 3+Knux, with the same ingenius level design. Imagine Green Hill Zone with every blade of grass swaying in the wind, running through gorgeously styled and rendered levels and awesome moving backdrops. All running smoothly at 60fps please. Bring back the elements such as "Robotnik", Robotnik bosses at the end of levels, chaos emeralds, animal-based robot enemies (containing fluffy creatures), Metal Sonic and keep the playable cast limited to something along the lines of Sonic, Tails, Sonic + Tails, Knuckles and maybe Espio thrown in there for good measure.
It'd be a sorta traditional Sonic game with next-gen 2D graphics and the possibility for some absolutely massive and stunning levels.
Hell yea, with online level races against others. Like Sonic the Hedgehog 2's 2-player mode, but better.