You're absolutely right -- _Conatantine_ is most definitely NOT a great movie. Perhaps not even a good movie. But, at the very least, it has more going for it than, say, _Daredevil_. I mean, Keanu does have his 'bad moments', but Ben Affleck has nothing but bad moments. In ALL his films. IMHO, of course.
But, yes, I agree: Tilda Swinton's androgynous, neurotic Gabriel was one of the film's brighter lights. However, I guess that we'll just agree to disagree about Peter Stormane's Lucifer. No big deal -- this is ONLY A MOVIE. And an inconsequential one at that. No????
As for the set being Animal House gone to seed ... well, Los Angeles usually tends to look rather rancid in dystopian-type flicks. (Think _The Terminator_, for example. Or some ancient Kurt Russell escapist fare.) But, who knows -- could be there's a not-too-terribly-subtle reference to _The Exorcist_ at play here???
Random thoughts ... It'll be interesting to compare this film with the up-and-coming translation from panel to pixel of Frank Miller's noir comic _Sin City_ (by none other than the immensely talented Robert Rodriguez, no less) We shall see.