OK. Mostly been said before, but will cover all necessary ground anyway.
ANCIENT Persia, not MODERN. THEY WERE CONSIDERED WHITE. Even Modern Persia (now officially called Iran, but Persia is sometimes used too) has a good number of fair-skinned people. The majority of the darkness of their skin comes from living in a desert.
Persian artwork (e.g. http://en.wikipedia.org/wiki/File:Mehmooni2.jpg) shows people with whiter skin than the Prince of Persia games.
Most important point is that it's BASED ON A GAME SERIES. What people who do mention this fact are missing, however, is that the "Sands of Time" trilogy are based around a different Prince from the one shown in the early games. Just like the Prince in the 2008 Prince of Persia game is different from both. This movie is (like the new game they're making) linked to the "Sands of Time" storyline. In which, as the several box-art screenshots have shown (here's my link: http://en.wikipedia.org/wiki/File:Sands_of_time_cover.jpg ), the Prince is WHITER THAN IN THE MOVIE ANYWAY.
Mr. Unknown "independent" filmmaker: Do your research.
On the topic of Avatar, first article I saw about the issues there showed a shot of a very white-looking almost perfect match for the cartoon actor playing the part of Aang. I'd assumed that THIS actor (the only one pictured in the article, which made no reference more specific than "white actor cast in non-white role) was the cause of concern. Having heard nothing else of note about the film, I was understandably confused about how this image offended people. Now that I've seen shots of the actual offenders, I can REALLY see where the problem lies. Stupid news websites. They need to do their research better too.
EDIT: On "Caucasians" - here's a map of the "Caucasus Region". You know, as in "Caucasian: A person from Caucasus" - yea... http://en.wikipedia.org/wiki/File:Caucasus_region_1994.jpg Pay close attention to the bottom right. That says "Iran" folks.