I haven't come to these forums in a while, but I decided to poke around and came across this thread.
I'm exactly like you Beef. I have 5 distinct 'universes' in my head, each with its own novel, one universe is a clearly defined trilogy in my head, and one universe, an urban fantasy, I've thought of ideas for 5 individual books now. But when I try to put them down on paper... It's just hard. I only get about 2-4 chapters in before giving up and either experimenting with another idea, almost feeling like it has gone sour. But the thing I've started to tell myself recently is that, yeah, the ideas my seem sour to ME, I've been running through them over and over again like a song stuck on a loop, but the REST OF THE WORLD has yet to hear of it.
Take my urban fantasy, I recently had written to chapter 6, and realized there was a scene that was stale, not much was happening, but the reason it was stale was because of how I started the book. See, my main character is a private eye, like Dresden, but he had fallen on hard times. Initially I had begun my writing sort-of how meg is suggesting, with an average, everyday activity for my main character. I knew WHERE I wanted my plot to go from there. So I had him hunt for a lost cat in the park. It wasn't very exciting from a reader's perspective, which is why I cut it later, but starting with him hunting for the cat and rescuing it from a tree, I was able to lead into the other elements from my story.
Once it was established that that arc with the cat needed to be resolved, I realized it was an inessential part of the book, but I had doled out 5 chapters after the cat scene.
(I've been going to another more active writing forum, and You can see exactly what i'm talking about as I posted a before and after
http://www.writingforums.com/fantasy-sci-fi-horror/120326-urban-fantasy-first-chapter-revision.html )
I don't really know if I... helped... any more, I basically repeated what meg said, or rather confirmed that what she suggested worked for me, and my brain seems to be wired the same way as yours.