4. The Amalgam Universe (Marvel + DC)
Sure, this one's about as likely to happen as Jimmy Hoffa's body being uncovered tomorrow, but the Amalgam universe is a particularly fascinating alternative to conventional Marvel and DC comics, with both sides agreeing to merge their signature characters together. For example, Batman and Wolverine have been combined to create a new character called Dark Claw, Superman and Captain America have become Super-Soldier, and so on. It would likely be too weird for mainstream audiences, but there's no denying the inventiveness of the source material, and how cool it would be to see these characters in a live action movie. It would make virtually no sense with regard to present continuity, but whatever...