Well... the first one, anyway. The second film went into "wants to be the cartoon series, but not using the cartoon characters" territory. At least the third one had a nice "Tales of the TMNT" style plot they kinda messed up.
Seriously, the second film was disappointing when you look at it from an adult comics fan attitude. The first movie followed the comic, not exactly to the letter, but with reasonable enough substitutions based on how they'd fit in a movie. Some characters get switched around, but it's essentially a story arc from the original comics. Some small influences from the cartoon were added out of necessity. Nothing more than April being a reporter, the turtles having colored masks, and "Cowabunga" being their catchphrase at the end (when it's only Mikey's, and has ONLY ever been Mikey's and only in that iteration). The second one devolved into wacky cartoon kiddy time. I blame New Line Cinema for kowtowing to the angry parental groups. Casey Jones tossed aside for being inappropriate to be replaced with a generic karateman that didn't offer anything. That... Vanilla Ice thing that's not even So bad it's good bad. And of course, Shredder turning into a Disney Villain/1980's-90's video game end boss (the kind that you have to fight twice, and the second time it's inexplicably bigger). Not to mention replacing April with a more cartoon looking version of her (the first movie managed to have the comic book version's frizzy 1980's Cher hair) and cutting an awesome nod to the Utroms because kids would confuse him with Krang. Yeah. No... Raphael being constantly angry instead of being one of Rob Paulsen's signature jerk characters and Mikey being a goofball instead of a laid back surfer... no... that wasn't confusing at all.
Tokka and Rahzar are the only good thing about the second film. And maybe that weird cameo by the Bart Simpson cup and the "A little too Raph" line.