Here's an idea for you.

Sonic Riders 2 would be kick @$$ awesome if:

a) They make the story about as long as SA2 or longer

b) Give a little more explination to the new characters (be sweet if Jet, Wave, and Storm were not only the descendants of genies but genies themselves)

c) Two words: Online playability. Think about it. There'd be regular SR2 and then depending on the system you have (most likely PS2 and XBOX cause Gamecube wasn't good enough to recieve that special ability) there would be a live version of the game where you can create your own racer and compete in races with REAL people. It'd be like Halo with a Sonic and racing twist!