Hands-down, the Game Gear was the #2 system. And this is coming from a Lynx fan. I bought a Lynx in the early 90's and loved it, but it had a serious lack of 3rd party support. Nearly everything on it was Atari games and arcade ports. That being said, I had a lot of fun with games like Warbirds, Rygar, Ninja Gaiden (arcade) and Klax.
I come across Game Gear stuff regularly in the wild and have picked up a couple of systems over the years. By comparison, I've never come by a Lynx system anywhere and have only seen Lynx games for sale at retro game stores. My local Goodwill always has Game Gear games for sale. In fact, I was there last week and there was a Game Gear system on the shelf.