Avatar is somewhat better written I suppose (though I haven't seen the new one or most transformers movies).

Also James Cameron had made movies that are pretty acclaimed. Even aside from Terminator and Titanic, there is Aliens and T2.

James Cameron is still not quite as good a filmmaker as some of the ones you mention, but he has still made very good movies. Also, he's made groundbreaking advancements in CGI, underwater filming, and special effects. So even aside from the quality of the films themselves, he consistently has fantastic visuals (and that tech is later adopted by other filmmakers)