The best WWI movie for aviation was Howard Hughes' Hell's Angels, worth it alone for great footage of vintage planes in action. But even beyond that, it exceeded my expectations. The special effects, especially for the Zeppelin scene, were way, way, WAY ahead of their time. It is an absolutely great movie, and Jean Harlow is timeless in it. When filming began, it was to be a silent movie, but Hughes took so long and went so overbudget that talkies hit the scene before he finished it, so he re-did quite a lot of it as a talkie. Harlow epecially you can see was still incorporating a lot of silent movie techniques even though it was a talkie.
Flyboys was enjoyable ... fairly accurate (except for the all-red German planes!!!{^) and ol' James Franco was surprisingly good in it. And The Blue Max is always good, even if it DOES star George Peppard! *ducking* But Hell's Angels beats them both hands-down, IMO.
Incidentally, anyone reading this thread who is looking for a really excellent though little-known book about WWI aviation, look for "Horses Don't Fly" by Frederick Libby. Very informative and entertaining read. Anyone intrigued by WWI aviation will love the book. You can get it on Amazon.
Ya gotta love those WWI German uniforms!