In the upcoming Thor movie, Idris Elba is going to be playing Heimdall, one of Thor's god buddies. In the comics the movie is based on, Heimdall is generally pretty stoic, just standing and watching over the rainbow bridge, the bridge between Asgard and Midgard (Midgard being Earth). He's stronger than some gods, just in terms of pure strength, but generally is just the guardian of Bifrost.
People have gotten upset over the casting of Idris Elba as Heimdall because he's black and Heimdall wasn't. It's a move that, well, makes some sense but in other ways doesn't. If we lived in a world where Prince of Persia had actual Persians and not Jake Gyllenhal or a world where the cast of Last Airbender was actually much more diverse, where one of the darker characters, Katara, isn't played by a little white girl (something that made me not realize who she was through the trailer until the end, when it dawned on me just how much of a difference it made), then casting Idris Elba as the traditionally white Heimdall would be a bad thing, just like those other things. But we don't. Instead, we live in a world where people wore black face and where Aang, Sokka and Katara are all played by white people. So, just casting someone of a different race is something that's done, so I don't see a problem from that perspective.
Now, should Heimdall in general be played by somebody not white? I don't think so if we were following the comics completely. But on the other hand, we're using the Ultimate version of Nick Fury in these movies, aka Samuel L. Jackson, so we obviously aren't copying the stories completely. Now, in the recent issue of Thor, the Mighty Avenger, they put in a black Heimdall, the first time a version of Heimdall has been black. In general, that's okay with me. It's an alternate universe of Marvel where an alternate version of Heimdall happens to be black instead of white. It's also fine in the movie. As long as the character is pretty much the same, I don't really care if he's white, black, orange or green. If he still acts the same and would do everything that regular Heimdall would do, then that's okay with me.
I didn't like Blackheart in Ghost Rider because he was kind of pathetic and stupid. He didn't seem a lot like the Blackheart I knew. Sure, he looked very different and didn't have his most recognizable form, but more than that, he was a different character. That's what made him unlikable to me. If they can make Heimdall the same character, whatever. If they make him a different character too, then it's completely idiotic. If he looks the same, then a different attitude is somewhat okay, if not good. If he looks differently, but acts the same, that's better, if not perfect (from my perspective). Hopefully, idiots will stop complaining and just watch the movie and try to enjoy it as a movie, not point out that Hogun the Grim is Asian and that Heimdall is black.