I've noticed some of those ripoffs were retroactive. They existed long before the Disney versions came out (most of the Fairy Tale ones), but were released only because they could get them cheap.
That's almost kind of like the whole BABE/GORDY thing: GORDY came out first, but BABE was much more critically and commercially successful that people consider GORDY to be a cheap ripoff... I like both movies myself - BABE is a more poignant and only slightly mature story, while GORDY is pretty standard Disney live action talking animal fair (though one interesting thing is the movie was written by the creators of GREEN ACRES, so that makes sense).
THEN, you've got cases of two different studios making ripoffs of each other, and each of them trying to beat it to theaters before the other (case in point: Pixar with A BUG'S LIFE Vs. DreamWorks with ANTZ).
EDIT: Actually, now that I think of it, is it just me, or does it seem like most CGI movies these days have become dumping grounds for B-list comedians to supply voices, insteading of bringing in A-list celebrities anymore? Seems like anytime an SNL castmate leaves the show, they end up supplying their voices for the next several CGI movies that come out. Then again, that's one thing I've liked in particular about Brad Bird's movies for Pixar, with some exceptions (like Samuel L. Jackson as Frozone), he didn't really rely on A-list celebrities, or even B-list comedians to do the voices... even on THE INCREDIBLES DVD, there's a featurette about the girl who voiced Violet, and she's not even an actress, she's like an author/historian (I think I saw a couple of her books in the store recently).