Don't let the naysayers fool you, Chronicles is one of the best Sonic games yet.
Bioware truly came through on this one. Let's start off with the story and characters. The story is one of the best one's I've seen in a Sonic game, as it deals with the past of Knuckles, Angel Island, the Gizoids and more. The new character, Shade, is extremly well done, much like Blaze of Rush was. As for the original characters, Bioware has improved on them IMMENSLY. No longer is Big a gigantic drool monkey, but merely a slightly dim comic relief character. No longer is Knuckles treating his responsibilty as Guardian like a joke. No longer is Amy's crush on Sonic at "psycho stalker" levels. I think you get the idea. Bottom line, Bioware took what was wrong with each character, and improved it. If you can make Big less stupid, you are worthy of praise, and Bioware did just that.
As for the battle system, it's pretty good. It's standard turn-based, only using solely the stylus. You can use special skills called POW moves to help in battle, and trust me, you'll NEED POW moves for some of the boss fights.
It's hard to find something to complain about in this game, but if I had to say anything, it'd be the music. It just isn't up to par with the music most Sonic games have used, but it's not really a bother, mostly since the battle music makes up for the bland field music.
Ultimately, Chronicles is yet another fine RPG from Bioware. This was there first foray into JRPG territory, and they did great. If you're a Sonic fan, an RPG fan, or both, you owe it to yourself to get Sonic Chronicles.