I remember watching some of the behind-the-scenes stuff on the DVD. He is indeed passionate but he's an example of what happens when you hand someone the keys to the car that's a little too keen and let them do whatever they want.
He thought he was writing Alien history so he went bananas with it.
I love his work. I was reading above about his disdain for the Resident Evil fanbase, but from watching the special features, it seems the that CamCom (fact check - it was cap com, right!) were entirely supportive of his vision in that the Alice idea was an entry level concept... you don't have the baggage and history of all those games. I've never played Resident Evil, but I love the movies.
On ChanceVance's point - I'm not sure that AvP was the movie he wanted to make. I've always thought he had bigger ideas and, if you look at his pitch documents, I reckon the movie would have been quite different if he HAD been given free reign and a bigger budget.
As it was, he made a great looking movie in Prague warehouse for about 50p. And it did what it said on the tin... I get that we'd have preferred something based on the game or the comic, but as I say... I'm sure that he would have wanted to do something much wider in scope than what we got.
He IS a populist film-maker and I love that - I've not seen a film of his that I haven't enjoyed (funny enough, as big fan or Romans and gladiators and all that, I thought "Pompeii" was one of his weaker efforts).