TMNT is the definition of crap
Going into TMNT, I do not think anyone would be expecting much from this game. It's a licensed game from the most recent movie that bears the same name.
Gameplay
TMNT is a platformer at its core. When you begin the game you only get a choice of one of the turtles, but as you progress, you play as the others and can seamlessly switch off between them at any time. There are also combat sections spread throughout each level. Most of the platforming works pretty well, but after the first few levels it gets...really...really...boring...and...repetitive. The combat in the game is almost unbearable. Every time I walked into a room and it said "FIGHT" I almost committed suicide. What the fighting boils down to is quickly pushing X and occasionally Y and then all the enemies are dead. The game throws a ridiculously large amount of enemies at you and it takes too long to kill them. Another big problem that I have with the platforming is that if you jump and you're too close to a wall then your character will do a wall run, which MANY times can lead to your death. The game consists of 16 levels and without giving away too much, has a big boss fight at the end.
Each character also has a unique special ability, but these can only be implemented in certain places for the most part and are otherwise useless. There are also special co-op attacks. the turtles can propel each other to jump higher than regularly possible, and they can do special attacks to enemies but I didn't find this aspect appealing or useful.
Story
UGH. Do not even get me started on this games story. Honestly I didn't even bother to pay attention, I assume it follows the plot of the movie but I never saw the movie so I don't know. They also seemed to mix in a few CGI scenes from the movie by the looks of it.
Replayability
I'm gonna to ahead and say that this game has about zero replayability. Half way into the game, you'll start to think you've already played these parts and you will NEVER want to play this game again. There are coins spread out through the game but the only ensentive to grab them is to unlock little cheats and stuff, but you'll get almost all the coins on your first play through even if you don't try. You also get a letter grade for every mission, but there is almost no care about those.
Achievements
This game is a very easy game to get all the achievements in. You will get all 1000 in one playthrough virtually just by beating the story. If you want some easy gamerscore then rent this game, you will definetly get all 1000.
Final Thought
This game is not a buy for anyone even a huge Teenage Mutant Ninja Turtle fan. The game just isn't good, plain and simple. Don't buy it, rent it for the achievements or if you are interested in playing it.