Even some of other characters, managed to find a certain niche they could exist in that used that formula in new ways. Tails had even more of an emphasis on speed, since he had to race another character to his destination, and Amy was constantly chased by one of Robotnik's robots, so she had to be constantly reacting to his movements, and quickly looking for methods of escape. While each of the modes was brought down by other problems, the basis for something potentially great was always there.
Because of that basis, I can still enjoy Sonic Adventure even after all these years. It may not have aged very well, but its still fun to play. Most importantly, combined with the Daytime levels in Sonic Unleashed, it can give me that one shred of (maybe foolish) hope that we'll see a truly great Sonic 3D game one day.
LOOK WHO CAME: