I really do not like the sound that come out of Bose headphones, so I invested in some Sennheiser in-ear headphones. I have a pair of IE80's with 3M Comply Foam Tips that do a great job of isolating most the noise (note that I like some low-level background noise when I sleep, I cannot sleep in silent rooms). They're not cheap heaphones (more than the Bose) but I use them as my everyday headphones and the sound that comes out of them is stunning. The 3M tips are also expensive as they need to replaced every 4-6 weeks if you use them daily, but they're well worth the cash.
As for sleeping in planes with them, they're fantastic. They sit just inside my ear and don't protrude. I can lie on my side (as I do when I sleep) and they do not fall out. They're not uncomfortable and I can play some music to drift off to (which I also required).
Either way, i'd head for in-ear phones over these 'sleep' headphone options. Just find a pair you like and that has the sound quality you desire.