I always and forever will consider myself a Star Wars fanatic, as opposed to a Trekker.
However, a Trekker friend of mine (my old physics professor) did share some strong opinions as to why Star Wars wasn't written nearly as well as Star Trek, and the prequels do suggest that that is the truth...
The Languages...
Chewie growling is one thing, cuz at least we could get some sort of inflection from the growl. And Greedo's Huttanese was even a little sensible, but the languages of the prequel universe really stink... I mean... really stink. Some are just innate squeaking and buzzing. Some are just obviously bad.... Compare that to the care that is taken by the Star Trek powers that be in crafting Klingon and Romulian etc.... almost unquestionably, Star Trek has taken more time in the crafting of cultures.
The Sith...
As many have already mentioned, the Sith just don't make sense philosophically. And why do two of them pose such a threat to the peace of the entire galaxy? Furthermore, why do the Jedi seem so weakened by the Sith? It's like Captain Planet who has sworn to fight against polluion but can in NO WAY touch it or else he is Kryptonited. What about the Sith makes them more evil than say.... some /other/ evil guy? Are the sources of evil different? Is not the force surrounding everything?
The Jedi...
What exactly /are/ their powers? We see Luke lifting rocks, and we see Maul flipping switches. We even see Yoda almost crushed by a pillar of stone by Darth Poopoo -- YET (for example) in Episode Three, little bug-like droids are on Kenobi's starfighter, and he doesn't just USE THE FORCE to remove them... instead, Anakin flies up next to him, tries to bat them off with the wing of his ship, and damages Kenobi's fighter... I don't get that. I thought the force would be the obvious answer to such a situation, and I called it out loud at the premier showing: "USE THE FORCE DANG IT!!?!?!" Furthermore, in the beginning of Ep 3, the ship that Anakin, Kenobi, and Palp are in has broken in half and is hurdling toward Coruscant -- why didn't they just use the force to stabilize it? SIZE DOESN'T MATTER.... Lucas probably should have thought about that one before writing it into the script, as fantastic a movie as Empire Strikes Back was....
The Politics...
We have hundreds upon hundreds of planetary systems -- we're talkin' thousands. And they have a galactic tribunal of rainbows and wonder in a room filled with floating chairs.... Uh huh... It takes the United States HOW long to make a firm decision on things with the filibustering and gerrymandering of districts, yet handing over dictatorship to Palpatine was almost instantaneous... Who the hell do they elect to govern entire planets?? And what's the deal with domestic planetary politics? They clearly state that Amidala was 14, and was ELECTED queen.... wh oelects a fourteen year old IN A MONARCHY?

Someone needs to explain that system to me...
The Force Hates Emotion...
I'm glad someone else brought this up -- but why is the Force against people having emotions? I guess in order to be a jedi you can't be anything but robotic.... This is just TeH stupid. End.
If Droids Had a Mind of Their Own...
Excuse me Mister Lucas...but they do... you make Kenobi say that stupid flippin' line and you ruin my enjoyment of C3PO and R2D2 almost immediately... Droids in your Star Wars universe DO have a mind of their own... C3PO OBVIOUSLY thinks for himself, and so does R2. What the heck, man??? They always told me to read my work AT LEAST three times before handing it to my teacher...
[/vent] okay... Now that al lthat is out of my system, I still think Star Wars kicks ass over Star Trek, but whatev' =)