Guilty Crown is an examplary demonstration of how important good sound design is.
Pretty much every aspect of this show rips off other more competently written shows, most strikingly Code Geass and Gurren Laggan. From Code Geass it steals the setting of a vaguely authoritative Japan currently in the midst of a major rebellion, and from Gurren Laggan it steals the not only the characters themselves, but also their whole arcs, interactions, and to some extent the plot itself. Although there's no point when MC Shu uses a galaxy sized mecha to punch the universe in the face so I guess the comparison breaks down eventually.
So Shu goes from leading a cozy, but somewhat empty life in safe but controlling Japan, before the anti-authoratative rebellion forces Shu to mature and come to terms with the dangerous, but very magical world around him, in the hopes of catching up to the mentor he's subtly jealous of and ultimately discover just how deep his and his friend's origins go and...look, I don't want to spoil, so just trust me when I say that either the writers of Guilty Crown were heavily inspired by Gurren Laggan, or the victims of chaos theory. I'd honestly accept either answer.
The question become then why I hold this show in such high regard, if it comes off as mediocre at best, and straight up plagaristic at worst. And the answer is the music. Now, you may claim that I'm exxagerating when I say that the composer's vocalist sings with the voice of an angel, but I challenge you to find anything more heavenly that Euterpe. Seriously, stop reading this, look it up right now. I'll wait.
Sure, Guilty Crown's plot is mediocre, and it's characters are kinda dry, and everything's dripping in that classic anime angst but when the vocals are pumping through you, and the instrumentals egging you to fight the gods themselves, can you really deny them? I mean, maybe you can, but you can at the very least listen to the soundtrack.