The soundtrack, for the 80's indie rock songs, that's not bad but it's corny.
The ambiant songs are good tho. That's what I use when I want to remember the movie.
The appreciation of the movie is like all teenagers cult classic (Breakfast club, Dazed & Confused, Kevin Smith, Superbad,...). The movies aren't so good but they had some good qualities and a personal or coherent universe that speak deeply to a certain demographic/timelapse.
For qualities, Donnie Darko got acting, some humoristic dialogues and ambition in the script and camera use.
It's overrated in the sense of pure quality but the fact that these flicks got more love than better movies means something that can leads them to classic.
Donnie Darko is a little bit too corny and sometimes boring to be in the list tho.