Originally posted by: TheRedEye
I only know of 9:
Euro Cup Soccer - Art was done, but the engineering never got far enough for there to be a game to find.
Matchbox Racers: This game was completed, but no copies have been found.
Monster Truck Rodeo: All of the screenshots we've seen are obviously mockups, may have never gotten past concept. I scanned a flyer.
Noah's Ark: As you pointed out, Konami put this out in Europe. The NTSC version got far enough along that GamePro actually reviewed it, but their review cart was not in the archives when they were mined. Was playable on Game Boy too.
Pyramids of Ra: Found and dumped! It's in a transitional period where it's still using black and white Game Boy graphics, but it's playable and fun.
Ring Raiders: Like Monster Truck Rodeo, everything we've seen was obviously in a mockup state. I scanned a flyer.
Sir Eric the Bold: A demo was made and shown at CES, but it never got very far. Was playable on Game Boy too.
Urban Convoy: Same as Monster Truck Rodeo and Ring Raiders. Flyer scanned.
Web World: Same as Monster Truck Rodeo, Ring Raiders and Urban Convoy. Flyer scanned.
And here some rumor mill-ish/alternate title stuff:
Matchbox Lightning: This was in a couple mail order lists back in the day, was probably an alternate title for Matchbox Racing.
Scarabeus: Alternate title for Pyramids of Ra.
Tune-Up Rallye: One of the first Matchbox games announced, this was either a vague concept like those other four or an early title for Motor City Patrol (released) or Matchbox Racing.
There are a lot of unreleased Matchbox NES games.
Matchbox Racers and Sir Eric the Bold hope that one day a prototype will be found.
I have never seen a scanned flyer of Ring Raiders. Is it uploaded?