As far as epic failures go, that list is rather tame and I think the Game Gear really doesn't belong there (sales of 10 million units cannot allow it to be considered a failed system). Certainly the game system that no one can argue with on that list is the Virtual Boy. I only got to try it at the CES that it was introduced at and it boggled my mind that anyone could find that experience worthwhile on any level. Cumbersome, headache inducing, expensive, monochrome (in a weird plasma shade of red)... what were they thinking?
Some systems that were outright failures or never reached their potential (usually due to poor marketing, manufacturing issues, lack of developer support, bad timing, etc.):
3DO
Virtual Boy
Sega Nomad
Sega Saturn
Neo Geo
Atari Jaguar
Turbografx-16
Nuon
Commodore CD32
Personally, I found the Dreamcast to be one of the best system launches in recent memory. The games were fun, with a high percentage of A-list titles. It was more a victim of bad timing (PS3 and Xbox were right around the corner) than anything else. CD and modem technology was already behind the curve, giving the system less pizzazz. I thought it was a pretty cool system, though. Very impressed with Bernie Stoler's handling of the whole thing. I think he gets a bad rap.
Neo Geo... Did you ever see the inside of one of those systems? I think the circuit board was the same board used in the game cabinets. I am almost certain the game carts were just repackaged version of the arcade carts, which were designed to swapped out. They obviously put too little R&D in cost reducing the system. $150 for a game cart is pretty whack.
Nomad was an awesome idea -- essentially a portable Sega Genesis that could use Sega Genesis cartridges -- but I have never seen one work 100% all the time and were impractical as a true traveling game system: battery life was abysmal. Game compatibility was not a 100%, either. But you could plug that baby into a wall and have a lot of fun with it when it did work.
I worked on a Nickelodeon TV show called "Total Panic" where I used to work on the video game segments. If you would like to see some game footage from some of these vintage systems, just go to:
http://www.micontv.com/html/total_panic_companion.htm
And look at the Video Game Roll-ins. I even have video from Amiga games that we also reviewed on the show.