It's fun, fast, and catchy!
THE GOOD: A brand new 2D Sonic game, great music, great 2D graphics, adds new abilities from the 3D games into 2D gameplay, extra characters add length and change how the levels are played out.
THE BAD: Kinda short when compared to Sonic 3 and Knuckles, getting the Chaos Emeralds is extremely tough, some parts of the levels pose too much difficulty for some characters.
When you think of Sonic, you think games that could have been better. Specifically the 3D games. Sonic Adventure was a glitchy mess, and while Sonic Adventure 2 was a lot better, it went downhill once again into garbage territory. What happened? Sonic stopped playing like Sonic. No longer was he going as fast as he could thru imaginative levels, getting Chaos Emeralds using bonus rounds and fighting one on one with Eggman. Instead, stories broke up the action. But let's forget about those 3D games and go back to the day Sonic entered the new millennium (and Nintendo consoles) with a bang: Sonic Advance.
Sonic Advance is just like his old Genesis games, except with brand new levels. It's in a 2D perspective and Sonic can go left and right as he pleases. He can jump and spin attack as well. But he has new moves, thanks to the B button of the GBA. Borrowed from Sonic Adventure 2, he has a new kick attack and can now ride rails. Sonic is not alone, as three of his friends have joined the party. The each control great (except Amy) and actually do give some replayability.
Although it plays a lot like Sonic the Hedgehog 3, it has a very different art style, the same one used in his modern 3D games. So Sonic has green eyes, solid blue and a lot of personally. His animations are very impressive and there are a lot of them. A lot of care was given to the graphics. The environments are also impressive, with lights, scrolling backgrounds, and a lot of things happening at once. With no slowdown at all neither.
The music is also great. A lot better than the music from Sonic Adventure I may add. The songs are catchy and great to hear, with no vocals. All your favorite sound effects are here as well. The "ching" from the rings are translated perfectly to the GBA. Most of the music in the game is brand new, but you may find some music that came from past Sonic games, most notably in Dr. Eggman's final battle.
The game is fun, but not perfect as it has it's own share of frustrations. You don't have any of these problems when you are playing the game normally, but you will run into them when trying to get the Chaos Emeralds. When looking for them, you have to explore the levels, and the way the enemies are placed, you will need to use somebody other than Sonic to get the emeralds, as you will easily run into them if you are not careful.
The minigame to get the Chaos Emeralds is unpolished and because of that you will find yourself losing the game because you can't line up with the rings very well. You will have to reset the game many times because you only get one chance at the emerald. Amy is also hard to use, due to she being a very slow character, and the levels were designed for high speed. So you will find yourself many times trying to cross a loop-di-loop, but can't because Amy is too slow to pass it.
But overall, you won't be disappointed with this game. It's fun, fast, and catchy. It won't reach the standards of past 2D games, but it's better than the 3D Sonic games lately. I recommend it.