Well, they are.
:laugh:
Seriously, there were several reasons the DeSanto version didn't go - according to the man himself, 9/11 had a lot to do with it (travel restrictions, etc. and the sets were in Canada). Brian Singer was obliged to split his time with X-2 (eventually had to leave BSG altogether). Fox liked Firefly.
There are others here who can give full answers (I'm at work now), but that's basically a start.
I am
Dawg