Logarithms & Trigonometry - the Mathematician's Roleplaying system
Although this game had many innovations to bring to the hobby, such as the novel combat system: (weapon skill)* log(sin(STR) * cosec(ARMOUR)) = Chance to hit (use random number generator) the verbose descriptions of mathematical operations and the complete absence of characterisation were thought responsible for this game's demise.
Pretext - the Philosopher's roleplaying gam
Unfortunately, the designers of this game did not appreciate the fact that a RPG should give the players a consistant reality to game in, rather than give the players the task of defining reality from scratch. So, while the players could make Force Assumption and Affirm the Negative rolls, the others could simply make Counter-argument and Metaphysical Implication skill checks, so the game would proceed nowhere.
Call of the Earthworm
In which the players took the role of soil biologists, investigating mysterious pH imbalances in soils all over the world. It took a very skillful GM to maintain tension over a long campaign.
Dungeons, Dragons, Sorcery, Big Magic Swords, Hordes of Orcs, Elves, Dwarves, Towns being Razed, Sacks of Gold and Gems, Large Epic Battles, Being Hired by Lords to find missing Artifacts, Talking to Innkeepers & Stealing Stuff (DDSBMSHOEDTRSGGLEBBHLFMATI&SS)
This game was generally thought to bring little in the way of innovation to the fantasy RPG scene, and the lack of an easily pronouncable acronym played a large role in its demise.
Dad's Army the RPG
Unfortunately, the sample adventure in this game involved the players coming head-to-head with a crack squad of German paratroopers, hence it only lasted 10 minutes and tended to put people off the game.
Schutzstaffel - the SS Roleplaying Game
This game took the roleplaying world by storm, as until it was released it was thought (and, in fact, proven by several game theorists) that it would be impossible to create a game too dark, bloody and distasteful for the gaming community at large. Nevertheless, the game sold well in its first edition and copies are still much in demand in certain European countries.
Greatest American Hero (The Superhero RPG)
Unfortunately, no-one could play this game because it didn't come with any instructions, just a lot of pictures and vague hints.
Limited Edition - The collectible trading role-playing game
As it worked with cards and even dice, the makers of this game reasoned that a RPG based on the players continually collecting the game aids and rule-books in order to improve their characters would be a commercial success. It did only reasonably well before it was bought by TSR just before the release of their new game, Advanced Dungeons \
Gary Gygax's Mythus
This one was just f***in' uplayable.