Sega admits Sonic is falling

[GrooveMan.exe]

Then that would only inarguably apply to Sonic 2006.

Sonic Adventure 1+2 were solid games with varied and fun gameplay.
Heroes had good gameplay spoiled by poor collision detection and camera.
The only real flaw with the Rush games are the chances to die via pits if you're not familiar with level layout.
Secret Rings made the mistake of coupling gradually improving controls with a rapidly steepening difficulty curve; but is otherwise sweet.