I haven't really seen the later incarnations of the series.
I grew up with the 87 series, albeit it didn't make it to the uk until around 89-90.
I loved the turtles in a big way when I was 8-10, collected the figures, had posters on my wall, had a Raphael costume etc, my best friend even made me four turtle statues out of plaster of paris which he painted himself. I played the tmnt arcade game whenever I could, and and we had main game for the amstrad computer too. My brother even read me turtles commics describing the pictures (he actually used to do a pretty good shredder).
I watched what I now know to be the first two years worth of episodes avidly and could quote a lot of them, though when I later saw the episodes from season 3 (after the technodrome arose from the earth's core and got punted back into dimension x), I really was not a fan, the premise just seemed to be getting whackier, though of course by then I was about eleven or twelve and so my interests had got rather broader.
Even with the first two years worth, when I see episodes now I'm less of a fan. The humour is still there of course, (, and I appreciate the nostalgia, but I miss backstory, continuing arcs or any nuance in character and writing.
I've seen some cartoons from the eighties as an adult, EG the first series of the Ewok's cartoon or dungeons and dragons, and while they're childish in parts I've still appreciated the writing, the level of characterisation, the world and the stories created, but others I see now and slightly shake my head at. Turtles is in that category.
lovely nostalgia, but not a lot else.
My feeling for the tmnt films is sort of the same, even though they tried to be somewhat darker.
I haven't really seen any of the later series, I could imagine them doing a good update, as they tried with the 2002 series of Heman, but I've never gone back to find out really.
With our dreaming and singing, Ceaseless and sorrowless we! The glory about us clinging Of the glorious futures we see,
Our souls with high music ringing; O men! It must ever be
That we dwell in our dreaming and singing, A little apart from ye. (Arthur O'Shaughnessy 1873.)