I recently downloaded a GBA ROM of Sonic Advance and played it on the VBA GX emulator for the Wii. Sonic Advance was the first original Sonic game on a Nintendo device since the demise of the Dreamcast (2nd Sonic game if you count the GCN port of Sonic Adventure 2). The game's plot is simple: Eggman is going after the Chaos Emeralds again and Sonic and his pals need to stop him.
In this game, you get the choice of playing as either Sonic, Amy, Tails or Knuckles. All of the characters have different abilities like Sonic can use the Insta Shield, Amy can use her Piko Hammer, Knuckles can glide as wellas punch and Tails having flight. You can choose between those characters and play as them, but even if you complete the game with one character, that doesn't mean that all zones are unlocked for all the characters. I don't know why they did this, but I guess it encourages for multiple playthroughs. There are also Chaos Emerald that need to be acquired. To do this, you must find a Special Spring to go into the Special Stage to get the Chaos Emeralds. Getting all 7 Chaos Emeralds and beating the game will give you access to the true final boss of the game. You can only be Super Sonic so collecting the Emeralds as another character will not let you access the final zone as anyone else but Sonic.
The good parts of this game would have to be the inclusion of Chao Garden, the music and the feature of multiple playable characters with different abilities.
The problems that this game has includes the slowness of the characters (especially Sonic), the over-usage of boost panels to try to make the game faster, bad enemy placement in later levels and somewhat poor level design. Sounds like Dimps didn't do a good job with their first Sonic Advance title, did they?
While Sonic Advance isn't bad for Sonic's first GBA game, it is far from being the greatest game. This game is okay at best but I prefer the sequel of this game to this one. If you want to play it, it is available online to purchase and you can get a ROM for it, but if you are not a fan of slow paced games, I suggest you get Sonic Advance 2 instead.