Great Geek Question!
Speaking as a dyed-in-the-wool geek myself, this debate has been fired up for decades. Let's do a quick "Tale of the Tape":
42 year-old franchise
10 Movies (Soon to be 11)
5 TV series
3 Comic Book Series
1 Saturday Morning Cartoon
32 year-old franchise
2 TV Series (With a possible live action in 2010)
13 Comic Book Series
1 Christmas Special
So, what does this all mean? Well, nothing really.
According to our friends at Wiki, The Empire has conquered more movie screens than The Federation. However, more people have flown warp speed than hyper drive in the aftermarket (including VHS, laser disc & DVD).
And what do these stats tell us? Once again, nada.
Star Trek offers stories of modern problems wrapped in futuristic settings and the danger of interference with other cultures while Star Wars gives the audience a look into one messed up family and good overcoming evil (that is, after evil defeats good).
How does this answer the question? It doesn't.
It seems there is a definite line between the 2 franchises, but its a line fans are willing to cross for the sake of sci-fi. You can indulge your child-like imagination & wonder when watching Luke & the crew take on Darth & the boys or fulfill your moral barometer as Kirk or Picard or Sisco or Janeway or Archer boldly go where no one has gone before.
So which franchise has more fans? Who cares? As long as the force is with us then all fans will live long and prosper.
Grim likes Babylon 5 the best ;)