Not a bad game but completely failed to meet expectations.

User Rating: 6 | Sonic Riders: Zero Gravity PS2
Sonic Riders Zero Gravity isn't worse or better than the last.
It's basically a different version of the last rather than an enhanced sequel.
Even though the game isn't bad it still did not reach expectations.

Story: A strange meteor fell on earth bringing with it mysterious ring artefacts. One of these artefacts got close to a bunch of security robots and they all started going berserk.
The next day Tails found a strange artefact and decided to head for the city along with Sonic and Knuckles to investigate it, but upon arrival they were attack by the same security robots.

Game design: If you're interested to know about the story it's pretty random and pointless, The game's Graphics however is surprisingly incredible!
The environments and character animations are so sharp and smooth the last game pales in comparison, you will enjoy the visuals.
The game has a story mode from which you can play as team Sonic or Babylon Rouge, though Babylon Rouge tracks are pretty much a remix version of the normal tracks (just like the last game).
The game basically has the same modes as the last (Free race, Grand Prix, etc) with new ones being Survival Ball.
The game's basic set up is the same as the last so there is not much new here.
Character roster count is up to 18 (last game being 16).

Game play: Here is where it's completely different from the last game.
You will play as Sonic and friends riding extreme gears, though this time the boards run on Gravity points instead of air.
By Doing tricks or taking character's signature short cuts (Speed = Grind, Flight = Rings, Power = Destructible objects) you will fill up the gravity meter.
The Gravity meter will allow you to use gravity powers.
There are 2 gravity powers, one which is used to make sharp turns (stops time and allows you to select whatever direction you want to go) and the other which is gravity blast (where you burst forward trashing everything in your wake), both basically replace the sharp turn and boost from the last game but require more accuracy.
Even if you lose Gravity points your boards will still move, but you won't be able to use gravity power.
Another new feature is transformable vehicles. Character types have been placed on the vehicles (eg just because you choose Sonic doesn't mean you can automatically grind). There are certain vehicles for every character that can perform type moves, however you will have to collect rings in order to transform them to its true form (so until you collect enough rings you can't grind, fly or knock things out of the way).
The controls are a bit stiff but their not particularly hard to get used to.

Sound: The game has an interesting selection of sound tracks, Voice dialogues however (apart from story mode and gravity power) are recycled voices from the last game.

Sonic Riders Zero Gravity isn't a bad game, SEGA really did put some effort in this game, it's just that their ideas were bad.

The last game had potential and knowing that there was a sequel coming to it, here were the following expectations from the game:
- Increase in character roster (To at least 25)
- Increase in stages (if not at least include past stages)
- Increase in modes (Forget the story modes, they are lame)
- Online competition.
The game has not met ANY of these expectations. Instead they have gone on making a different version of the game with seemingly restricted controls, which is completely NOT what we wanted.

Apart from graphics the game hasn't improved at all and the game also lacks other famous characters fans were hoping for (Like team chaotix, Metal Sonic, Big the Cat .etc)
This game is a great disappointment, this makes me question if SEGA ever listens to feedbacks.