Sonic free riders: Zero Gravity is the sequel to Sonic riders on the gamecube. The game improves over the original in some aspects but fails in others.
The game improves in that it takes out the terrible pitstop mechanic from the original and replaces it with a part of the gravity system. Another improvement is the music with each song fitting the track perfectly and the main theme (Un-gravity) is another great crush 40 song.
Where the game doesn't improve is in the control department. Instead of using the gamecube controller you use the Wii mote. While the control isn't as bad as sonic and the secret rings its still leaves much to be desired. There is an option to use a gamecube controller but its hidden beneath menus and I didn't find out about it till I finished the game.
The game's story is entertaining enough in order to keep you playing until the end. Unfortunately its only a good story and barely good enough to keep you invested.
This games biggest change over the original is the implementation of Gravity controls. Instead of being able to drift around turns you now can manipulate gravity in order to make tight turns. You can also use gravity to fly along the track at extremely fast speeds. To keep this from breaking the game Sega implemented a gravity meter so that when the meter runs out you can't use gravity abilities. Their are only a few ways to restock the meter. These include: landing tricks, grinding rails, and collecting gravity points through power up boxes. Unfortunately the gravity controls are finicky. Making sharp turns difficult and races hard to win.
All in all this is a pretty mediocre game that I really don't want to play ever again. However if you're a hardcore Sonic fan then You'll probably get your money's worth out of it.