Sonic Battle is a fast paced pseudo-fighting game, akin to Super Smash Brothers from Nintendo. Rather than being 3D side-scrolling, this game employs a 3D isometric view- not a static, sprite-based field though, it is comprised of actual texture-mapped polygons. The character sprites are 2D though, and while you think it wouldn't work- it does :P
You can have 9 characters to choose from, 5 modes of play; Story, Battle, Challenge, Training, and Mini Games; you can link up 4 GBA's to fight your friends, each character has a bunch of moves you can use to beat the you-know-what out of whoever you're fighting. It has a system of selecting Aerial, Ground, and Guard based attacks, and depending on what type of attack you set for which area (aerial/ground/guard), you have a possibility of 9 total different special attacks to choose from (only 3 at a time in a match though) which you can change each time you lose 1 stock point.
Among the other many features, Sonic Team has also made the game more dynamic with the addition of a trainable character whose abilities and techniques you can raise and add to. You get to pick and choose every aspect of the robot's style (running, attacking, jumping, dashing, etc etc etc etc etc).
The game takes a moderate amount of time to play through as all the characters, and adds a longer lifespan to itself if you wish to play through and beat it completely (all characters, get all moves for the trainable robot, etc).
There's one major difference between the Japanese and US versions of the game: The voices. While both games allow you to choose the language for options and dialogue, the US version has completely different voices from its Japanese counterpart. The most noticeable difference is Tails, who has an almost female voice in Japan, while his US voice sounds... whiny.