My 2 cents:
TMNT I: Cool film. Not one of the best I've seen, since it still has lots of corny moments, but good. I bought the DVD last weekend.
TMNT II: Wow...I haven't seen it in years. I don't think I remember liking it as much as the first though.
TMNT III: My ONLY memory of TMNT III... It came out in theaters about 5 months after my parents divorced, so I was living with my mom at the time. She promised me, repeatedly, that she would take me to see it. To this day, I still have not seen this movie.
(TRIVIA: In the US, at least, TMNT I made more $$$ than the two sequels combined.)
As for anything you want to know about what the creators of the first movie have done since then, check out:
www.imdb.com
Oh, and the whole thing about "parents complaining"...I was 6 when the first movie came out, and my folks had no problem with it. But then again, they also let me watch "Gremlins" and "The Lost Boys" when I was 4, so...
(Hey, I just realized: My 3 favorite movies as a kid *all* had Corey Feldman in 'em. Weird...)
Peace!