Yes Game Gear and Sonic rocked. Too bad you had to play from an adaptor since battery life was non-existant
As for Ipaq check the real prices, not the rrp or high street prices. There is no hdd in an ipaq
For porting an emulator a permission is not good enough. If the device has very limited speed (GP32 at top 133MHz, but afaik that speed produces a battery life experience similar to that of Game Gear fame...) most parts of the emulator has to be rewritten in assembly, and even after it can still be bad.
On the contrary the bottom line speed for a pda is 200MHz and it is designed to be used for hours. Since similar architectures are being used the clock rate comparison is very fair in this case.
For a pda if you are looking for something, chances are somebody already done it. For GP32 somebody might sometime do it or you are on your own.
I'd say GP32 is fun if you are prepared and able to do whatever you need on your own. Also consider speed, battery life and other limitations. If you are happy with that - imo the price is a bit high for an overclocked gba without any graphic acceleration - go get it. Otherwise get the PDA.
Or better wait for the new PDA models coming out this spring/summer making the 400MHz models much cheaper