It was quite a silly movie but dealing as it did with profound themes -- sacrifice, redemption, etc -- it has found its way back into my thoughts periodically ever since we saw it.
There's one particularly interesting discussion, about faith. Constantine is a faithless man: he doesn't believe in God, or Satan, or heaven and hell, any of that. He doesn't have to believe, because he knows. He was dead, once, for two minutes; he has seen what comes after this life. So, he knows. There is no possibility of doubt, for him.
He is denied the gift, and the burden, of faith. He is immeasurably diminished by this, somehow, to me, made less than human in some respects, but more than human in others.
I'm thinking that the Hellraiser comic books on which the film was based would be a great read. I'll have to check them out.