There is nothing in GL that comes even close to the depth of Loki's conflicting emotions when he learns of his true heritage, or Thor's heartbreak when he finally understands the full measure of his situation ("Can I come home?").
Eh, I wouldn't call any of that particularly "deep" myself. It was still all very surface-level, comic booky stuff.
I certainly won't argue that GL was very deep or complex, but then I never felt that way about Iron Man, Donner's Superman, Burton's Batman, or the first two Spidey films either. Those were all very simplistic movies as well, and yet most fans still manage to love those.
GL might not be quite at that
level, but I still don't see what it does that's so incredibly different either.