Did you read the ones written by Alan Dean Foster ("Dinotopia Lost" and "Hand of Dinotopia") Rachel? Those who are really good.
There are many others which I found to be of somewhat mixed quality (none really bad, but I don't recall having been utterly taken with one of them either).
I have!

Outside of Gurney's own work, those two are my favorite Dinotopia books. They're very well-written, for being that they were done by a fan, and not Gurney himself.
Not to say that the stories can't be well-written if you're not the author, but I was pleasantly surprised that Mr. Foster had contributed so much to the world of Dinotopia without it seeming non-canon.
Alan Dean Foster does this remarkably well, imo. Sometimes I go back and re-read both the first and second book.

As far as the other, smaller stories, I'd have to agree with you on that one. Some of them stand out, and then again some of them just don't. I've always been fascinated by the fact that Gurney allows others to publish books based on the world he created (as long as he read and approves it, which I think he does...) But some of the things that authors write about in the books are hard for me to consider canon. And I have to admit, when I read something that I don't think would ever happen in the Dinotopia world, I secretly choose not to consider it canon - even if Gurney himself did approve of the book being published. XD