TMNT shouldn't take you more then two hours to beat. That being said, it's a decent rental at best.
GAMEPLAY - TMNT consists of two basic actions: platforming and fighting. The platforming is pretty fun, the fighting, not so much. The game is set up so that you go around the level in basic platforming, similar to prince of persia where you scale walls and swing from poles. Then the game will put you in fight mode. So you're either running around the level or fighting, you can't do both at once. When you fight, you have the B button to do a basic attack, Y button to Kick, X button to do team attacks, A button to jump, and RB button to block. Later during the game, you will be able to do team attacks, all varying depending on which turtle you control. The fighting is dull, boring, and repetitive. Aside from the team attacks, there isn't much variety.
GRAPHICS - The graphics for TMNT have a comic book feel to it. Aside from the terrible looking environments and "flat balloons", it's looks good for a movie game and represents the turtles very well.
SOUND - Voice acting is decent. Soundtrack is bland. What sets it off the wrong way is having the turtles say things every five seconds that either isn't funny, doesn't make sense, or is said the wrong way. Hurts your ears and becomes very annoying.
VALUE - A decent rental. The game can be beaten in about two hours and the achievements are very easy, so easy a caveman can do it! After you beat the game, there is nothing else to see, unless you want to do the challenge maps which are a waste of time and are not important. What hurts the value is is two very important factors: online play and co-op play. It's two things you should expect from a turtles game and sadly, none are present.
In conclusion, TMNT for the Xbox 360 is a decent rental. It should take you about two hours to beat the game and get all 1000 achievement points. A good game for the gamerscore junkies out there.