I would not consider it unsuccessful tho. They supported it for a decade or so. It was a niche system. Neo Geo CD or Neo Geo Pocket Color those can def be contender for good systems that didn't succeed but Wonderswan would be added to that list. Personally I'd also add SEGA Nomad as it's the Nintendo Switch concept in 1995 and a near full library of Genesis games. (Virtua Racing did not work I believe)

Yeah, people often tend to forget that NEOGEO was arcade cabinet system first (NEOGEO MVS), one that was not only cartridge based (which was not standard at the time), but could have up to six cartridges installed in it, making it very profitable for coin-op arcade owners.

NEOGEO AVS was rental console version targeted at rental market - not to be owned. But once they saw how popular it is, they released it as actual home console. So it was an actual arcade cabinet in the home console packaging, not home console at all - hence the pricing.

My favourite unsuccessful system I grew up with - The Sega Saturn, got it for christmas 1996 and it was the best christmas I ever had, the graphical improvements over the Mega Drive were outstanding at the time and I couldn't stop playing it, a couple years later I got a Playstation but there's just something about the excitement I felt opening that Saturn that makes it stand out to me the most.

Honorable mention goes to the Atari Jaguar. I've been fascinated with this console for years for the spectacular failure that it was and it's small library of games. Most say there are no good games for the Jag but there are definitely some decent titles in there: Doom, Wolfenstein, Tempest 2000, Atari Karts, AVP, NBA Jam TE, Rayman, Super Burnout and several more. I always have the Jaguar hooked up in my setup and play it often, especially now that I got the Jaguar Game Drive, that thing is the best flash cart I've ever gotten, it even plays most of the CD games too without needing the CD attachment.

Got to stand up for my first console Master System.
Sega CD/Mega-CD also had an interesting selection of games, several gems there.

And from emulation experience: I wish WonderSwan would've seen international release.

Yeah if we include the PS3 on the grounds that it lost Sony literally billions of dollars and took them from dominating the market to barely scraping out of last place, then that would be my pick too.

Terrific console thanks to exclusives like Uncharted/TLOU/Killzone/Resistance/Puppeteer/etc plus most of the best third party games of the generation.