I made reference to a number of things that he'd written. When I looked at imdb.com it listed 'Dark Angel' under his writing credits. He wrote the story for the pilot and directed it as well as coming up with the concept of the show. As for T3 and The Sarah Conner Chronicles, I guess he allowed them to happen. But you're right, he didn't write them.
I don't think he's the worst writer to have ever lived. There are concepts throughout his films that I've really liked. Conceptually he's interesting, but I find his characters fairly one dimensional and some of the lines he writes for them to be truly cringeworthy. Particularly the male bravada type stuff.
Also I think that he overdoes the strong female I'm-going-to-play-with-the-big-boys character. There seems to be one in practically everything he writes. Aliens= the female marine who is always being ripped on for being a woman, Terminator series= Sarah Conner, The Abyss= Ed Harris' ex-wife, Dark Angel= title character. I don't mean to sound sexist and I'm not saying that women can't be the hero, but I just think he overdoes it that's all.
I'm a big fan of Philip K Dick (and Paul Verhoeven) on the other hand and regard Total Recall to be, by a huge margin, the best film that Shwarzenegger was involved with. I was surprised that people liked T2 more, which (aside from harbouring one of the worst teenage characters ever written) is chock full of fairly cheesy Star Trek/ Isaac Asmimov like dialogue about the relationship between humans and cyborgs.
I didn't mean to offend anyone, I was just surprised about how many people had voted for James Cameron films. To me he's kind of like an (admittedly preferable version of) Michael Bay.