I don't watch the show and haven't watched the movie - but these names are Japanese, then, right? If it is based on Japanese - then the correct way to say Iroh would be to pronounce it E-roh. I's in Japanese are always pronounced as a "E". Double Aa is like "O". Maybe the animation you so love mispronounced the names?
No, the series is an American
show made specifically for Nickelodeon, and based on certain Oriental lifestyles and martial arts techniques.
The Last Airbender's creators named their characters, and M. Night should have gone with their
pronunciations regardless of how he
thought they should sound.
Aang is pronounced with a long A, not with an O. Iroh is pronounced with a long I, not an E.
Regardless of how real
Japanese names are sounded, the show's American creators used specific pronunciations. To do otherwise just makes this movie even more of a blasphemy.