FreezeSMS is a multi platform emulator, which supports 5 platforms, including Sega Game Gear. It has a nice interface, supports packed ROMs. It use Direct X for emulating video, sound and joystick input. Saving function is available as well.

Fusion is another multi platform emulator, which supports Sega Game Gear. The interface is average, has enough setting for video, sound and controls. All you need is just to select in menu which platform you are going to emulate and press play.

Fusion Emulator Download 2

Not bad emulator for Sega Game Gear and few other platforms. It supports more than 90% of games. Supports saves and network game. It also uses graphic filters to make picture better in full screen mode.