Nintendo has always ruled the handheld game console market, since 1989. They've had many challengers, all have failed, with the PSP coming the closest to having real, long-term success. The Game Gear was a bright blip on the radar, but only that, as it didn't last all that long. Everything else was over quick.
I do wish they'd bring back the "Game Boy" name for their next, unless it really is going to be a so-called "hybrid" system.