Since the dawn of time there has been an intense rivalry between Marvel and DC comics (OK, maybe not quite the dawn of time, but you get the picture), so naturally, comic books fans have been practically begging the movie studios for a crossover flick of any description.
It doesn't have to be the entire DC universe vs the entire Marvel universe (although that would be freakin' EPIC), but perhaps a VS movie between the most powerful characters of each universe. Superman VS The Hulk anyone? So although this may never come to life as a real feature length film, tech-savvy comic book fans have certainly tried their best (and succeeded on several occasions) to make Marvel vs DC shorts on YouTube. My personal favorite has to be this one I've posted below, check it out!