It is really difficult as the style of his albums differs enormously. For example, in some repects Hey Stoopid is his best album as every single song is great and could be a great choice for a single. However, it lacks some of the nasty Alice that Raise your Fist and Yell oozes throughout. Both great albums but in totally different ways. Of course then there is the classic Welcome To My Nightmare album which is totally different again. Of his recent 3 albums I prefer Brutal Planet by far. I think Dragontown and The Last Temptation were a little weak in comparison.
I think my conclusion is that I don't have a favourite album as they are too different to compare and also because he has done sooo many! It is the same with Kiss. I can narrow it down but can't pick a favourite.