The 2nd wave of portable consoles is seldom talked about for some reason despite some interesting hardware coming out. the 2nd wave and handheld consoles included: The Neo-Geo Pocket (and the short-lived color version), The Sega Nomad, The Gameboy Color, the Game.com bubble, and the Wonerswan consoles.
The Gameboy Color, while not as hot selling as the Gameboy for obvious reasons, easily outside all their foes. The Neo-Geo pocket/Color was a bit mismanged and helped with SNK's bankruptcy, the Game.com was innovative, but Tiger really should have waited and launched a complete vision of the console instead of 4 different versions, the Wonderswan gave a bit of a fight but the lack of a launch outside japan along with Banddai not spending enough on courting developers brought it down, and the Nomad, while a portable Genesis, was only released in America and cost $180.
One thing to note is that, all the consoles of the 2nd wave of handheld consoles had some great games on them. So it's a bit sad that these machines are so seldom talked about.
Personally I liked the idea of the Game.com and it had some good games. It was an attempt to combine a portable gaming device with a PDA, and while they made numerous mistakes in making this idea successful, it was still an experience to behold. Outside of a multi-colored screen, the Pro-light model was the best we were going to get at an affordable price point for a PDA/Console hybrid.
The WonderSwan is a little mixed for me, I had got one from a store with a handful of games, about 6 of them were playable without knowing japanese of the 10 I got but they seemed to be even less than Gameboy Color levels at the time. When I eventually got a Swan Crystal some years later and another batch of games things were different but that was around the end of the machines life. I think the Woderswan was more of a pet project from Bandai than a serious entry. Rumor is, Bandai already could have put out a better graphics chip and sound chip, but cut corners. To be honest, I don't think that it's far-fetched to believe that, especially the latter. It has a good selection of fun titles, I just don't think Bandai took it seriously.
I didn't get a Nomad until around 2002. Stores were dropping the Nomad fast and in my area I never could find one for a long time. I ended up buying the one at a second-hand store. It's a portable Genesis, and it's bulky with poor battery life. Otherwise, it's a neat idea, but I think they released the NOMAD way to late to even grab a niche audience. NOMAD at latest should have came out in late 93 if they wanted to try a portable Genesis idea. Of course the Nomad uses the Genesis Library, which is superb.
Gameboy Color was ok for what it was. I think a lot of devs just kind of upgraded their existing game boy games to work with the colors, well, uh, color. But never really took advantage of the improved specs. Some games did and it brought in a breath of fresh air, but the GBC felt more like a stop-gap to me for the GBA to be honest. It still has some good games and also mostly complete BC with the original GB library.
Neo-Geo pocket was given to me by a friend who got it imported and no longer wanted it. Well sucks for him! Got the Neo-Geo pocket color at launch. While the NGP was no slouch, SNK really should have released the color version in the first place. The NGP consoles were supposed to help SNK with their financial issues but they made quite a few missteps. As I said before the NGP color should have been the portable released from the start. It was way too late for a B&W handheld to do well when the original NGP was released, which also was japanese exclusive. It's clear they were thinking they would grab some of the domestic market for some easy profit but that didn't end up happening. As a result the NGP Color came out worldwide while betting the farm, and it should have never gotten to that point. The NGP consoles had some great games from SNK and third-parties, including possibly the best portable Sonic game ever made (at that time). It replaced the D-pad with a mini joystick and that control choice was brilliant. Why nobody else though to take that idea, I have no clue. Also you get UI when you turn it on without a game, a neat extra touch.
These consoles are usually the least talked about when handheld discussions occur, however they all have some great games, very innovative ideas, and are great fun!