I like SOAD, partially because they got me into metal, and partially because they're just a good band to chill to. Depth and/or tons of creativity help a lot, but ultimately what makes music good is the way it makes you feel. If a band isn't all that original, but they can make me feel a certain special way, then I'll still really like that band. SOAD can sometimes give me a feeling that I really enjoy, especially when I want something I can just relax to, rather than lie with my eyes closed in soak in every detail, like I do with some music.
And if you need depth for good music, none of us should be listening to metal. Even the more complex metal bands are pretty simplistic compared to Beethoven and the like. I doubt that most people here (or anywhere for that matter) can even comprehend the depth and nuance of the great classical composers.