I would LOVE to see a GF movie.
There are however a number of problems with this, I think. Firstly, movies are quite a different medium than games. I agree that it would be hard to squeeze the plot of the game into a comfortable movie (perhaps go the Kill Bill way, though I think these drawn out things appeals less to non-fans.), just consider the time you spent playing (yes, I realize most of the time was just running around =P ).
This leads to the next obstacle, which direction would the movie take? I think it would be hard to include the game's whimsical interaction and humour between the "actors" and still be so dramatic at times. I probably wouldn't have a problem with it, since I know the game, but others might go into it expecting this or that.
Also, while we're on prejudices, this movie would most likely be animated. For some reason this is considered a bit childish (some peope still live in the sixties =P ), and would further scare away producers (along with the direction it would have to take, and the somewhat meager financial results from the game (signalling low interest).) Even if the movie was made and perfectly conveyed the feel of the game, I don't think it would rake in much money (What a child movie? With skeletons? Death and murder? And so on), the fanbase IS actually rather small.
On the other hand, with a dedicated team and someone with a few heaps of money laying around, I can defiantely see GF being turned ito a movie, it is a good story after all.
I'm sorry for all the ( )s, I know they are annoying. And I know my thoughts are somewhat rambling, I'm in a hurry. I'll focus more next time!