Do you have a preference for material/color choice? What do you consider "stylish"?
How much protection do you want? Remember that more protection usually means more bulk. Do you want built-in screen protection? If not, do you want other screen protection?
Do you need open access to all ports at all times? Do you regularly use accessories (such as docks or headphones with strangely shaped plugs) that require completely unobstructed access to any given port?
Do you want extra features (a belt clip, a stand for video watching, a wrap for your headphone cord, or even an external battery pack)?
And finally, what price range do you have in mind?
The answers will help determine what would be the "best" case for you
The least noticeable case would be the Power Support Air Jacket in clear. Best 30 bucks I ever spent on cases. Includes 2 screen protectors (these are top quality, not the cheap stuff thrown in), one glossy and one anti glare.
The case I have stuck to longer than any other case for any device I have ever had is the iFanatic iphone case. Its a leather case which offers good protection for the iphone as well as pretty easy access to it.
I think the 2G and 3G iPod touches are the exact same size. A 2G case should work with a 3G.I just bought a Contour Design 'Flick' case for my 2GB and I think this will fit into 3G.