Thanks everyone for the input and recommendations
So we went ahead and watched TMNT (1990) last night. Shinobi was right,
this is how you successfully translate an iconic cartoon or comic to the screen.
Not having any emotional connection to the source material, I was able to go in with fresh eyes and evaluate the film objectively. While the FX is understandable crude by today's standards, I thought both the cinematography and production design were very effective and appropriate for the film. I especially liked the depiction of New York City at the dawn of the '90s. Squint just a little bit and it could almost pass for Burton's architectural style of Gotham in
Batman '89.
I was also really impressed by the way both the voice cast and puppeteers were able to imbue each Turtle with a distinct personality. I can't speak to the faithfulness of the characterizations but I think they did a great job in differentiating each Turtle, and their respective personalities nicely complimented each other. And Splinter had such a wise, sad quality to him that it was actually touching. His loyalty to his 'sons' really got to me a couple times.
The action scenes were quite impressive too, considering these were in-suit actors trying to convincingly create martial arts sequences. The brawls were fun and the one-liners were silly but entertaining. I can imagine audiences in 1990 having a total blast with this movie.
And on top of all that, it had humor and heart. It doesn't have that cynical quality that so much '90s entertainment for kids tried to peddle. It's got something to say about friendship, family, loyalty, as well as self-acceptance and humility. Overall a good time and a pleasant surprise