Rings of Fire
This is pretty much Sonic as you remember it, though gussied up for the modern day. I don't really care if the animations look the same as the arcade/Genesis Sonic games; all I know is that the game's chock full of fun doses of adrenaline.
Standard Sonic fare, really: Push the blue blur in either direction to make him run; you can jump, rush (thrust -- whatever), and trick while in midair. The dude moves fast, and the level design is a total riot. This is one of those games that gets better as you become more familiar with the level layout, and if you have the patience for that sort of thing, you'll surely get your money's worth here.
I love the level design, love the "rush" of the game, and dang, if it still doesn't look fantastic on DS to this day. That being said, some of the bosses are a real pain in the backside -- not all of them, but some. Like any good boss fight, there's a process of figuring out its weak spots. However, with limited lives and a pretty unforgiving edge against you health-wise, you'll often have to redo an entire level when your extra lives run out.
A few bouts of frustration not withstanding, Sonic Rush is still excellent. Even the touch-screen mini-levels are great fun, and the sights and sounds of the game are sure to please anyone with a real need for speed.