3. Eternia
One of the biggest problems with Masters of the Universe '87, was the fact that the major plot took place on Earth. It wasn't the idea, or even the execution of this idea that was the problem---it was simply the fact that He-Man takes place on Eternia. Portals to other places have long been a part of the He-Man story---the animated series even visited Earth in the He-Man and She-Ra Christmas Special and Queen Marlena was established as an astronaut transported from Earth to Eternia---so the connection to Earth isn't problematic. What
is problematic is the fact that the core struggle of Masters of the Universe is the battle for control of Castle Greyskull between He-Man and Skeletor---on Eternia. In the 1987 feature film, this struggle is minimized both by the fact that at the film's opening Skeletor already has control and the fact that instead of fighting for Greyskull on home soil, they fight on Earth. This isn't to say that a reboot couldn't take place on Earth or even reference the Earth connections listed above. The fact is that in Masters '87, the first act was devoted to getting the team to Earth as quickly as possible and then the rest of the film is weighed down by gags that capitalize on the alien nature of things. Basically, it wasn't what fans wanted, it was used as an unnecessary plot device, and it cheapened the story. If there is one thing we've learned from screen adaptations in the last ten years, it's that the story has to be good or else the fans won't support it---remember Hulk? Yeah, I wish I could forget it too.