· Ant-Man
As far as I can tell, Edgar Wright and Marvel are still planning on making this film for release in 2012, which is fitting since a feature length version of Ant-Man would help ring in the apocalypse. Thankfully there is still time to fix this obvious mistake: Stay small (pun!), keep it brief and attach Ant-Man to Iron Man 3D. Simple!
· Aquaman
Thanks to Entourage, the only way audiences would believe in a full-length version of Aquaman would be if it was directed by James Cameron. And unless you transport Aquaman to Pandora, that probably isn't happening anytime soon. [CORRECTION: As the smart commenter below notes, Aquaman is a DC Comics character and not Marvel. The moral: There are too many comic book characters.]
· Deadpool
Besides the fact that Ryan Reynolds already has a superhero franchise (The Green Lantern; take that, Marvel!), there's the little fact that Deadpool was decapitated at the end of X-Men Origins: Wolverine, meaning future full-length movie prospects will be harder to come by. Oh sure, his detached head winked at the camera during the post-credits scene (yep, that happened), but just the marketing effort alone (1) to remind people who Deadpool is, and (2) to explain how his head got reattached, seems like a colossal waste of money.
· The Hulk
Marvel is 0-for-2 on adaptations of The Hulk and maybe that's because people best remember the character in short, episodic bursts. Think of the avant garde possibilities of an Incredible Hulk short film. Each one could consist of Bruce Banner trying to stay calm in the face of daily indignities, like commuting to work or dealing with TPS reports. Then, HULK SMASH and credits.
· Thor
If only Marvel thought of the short films conceit before greenlighting/spending millions on Thor. The list of box office poison-level offenses here is long: Unfamiliar character, weirdly un-comic book-y tone, ancient setting, a magical hammer. Poised to be Marvel's first dud, if there's any way for the studio to cut Kenneth Branagh's film down into ten minute chunks, surely they're looking into it.