I loved my Game Gear, but it's a bit tricky for me to justify getting another one as a retro pickup because:
- It's a battery vampire.
- The screen is a low quality LCD panel. There's some unexpectedly pleasant side effects with this, like the nice color blending that happens in games like Outrun and the end credits of Sonic 2, but it makes it a bit tricky to play fast paced games at times.
- The electrolytic capacitors need replacing. If left unchecked, the Game Gear's motherboard will be permanently damaged and eventually unusable.
It's a bit of a crazy idea, but you might consider taking the Game Gear's case and
throwing in a Raspberry Pi mod to turn it into an all purpose retro portable. That gives you the form factor, without the hassles of the original, cheaply sourced hardware. I've also seen some Game Gear console mods that looked quite nice on their own. Yes, I'm aware of the Sega Master System and the Sega Mark III, but the SMS never had the rich color palette of the GG, and the Mark III, the SMS and the GG all have their own nifty exclusives.
There are things I liked about the hardware, especially the Sega soundtracks. Sylvan Tale has a really nice chiptune soundtrack from the composer of Panzer Dragoon Zwei, Saga and Orta, and the Shining Force games have neat renditions of the Shining Force II soundtrack. The Sonic games sounded great, too, and Tails Adventure's a gem on its own merits. The AM2 arcade ports were excellent, the Phantasy Star spinoffs were interesting, the puzzle games were good, and some oddly excellent titles like Mick & Mack Global Gladiators, GG Aleste, Royal Stone and the Disney platformers showed off the kinds of animation and colors you could pull off on the thing.
If Sega wasn't cheap with the display and the caps, I'd have an easier time recommending it. Just beware that unless you're buying it second hand from someone that already replaced the caps, you'll need to do some maintenance if you want the hardware to last.