Meh... It's Turtles in Time, but there's not much else to it. It's ok, but it could've been so much more.
The other problem is that the game is much too simple, even on the hardest difficulty level, you'll finish the game inside an hour. As for the multiplayer aspect, you'd think that would've saved this game from mediocrity, but it doesn't. Mainly because even while you could be four on screen, you're all pretty much on your own as there's no real incentive to play as a team. Just mash that button and hope you take less damage than anyone else.
As it is, it's a game you can play with your kids if they're young and they like the turtles (though they may wonder who some of the villains are). Even if they don't, it's a good way to introduce them to the turtles. The only other people I could recommend this game to are those who have fond memories of TMNT 2 in the arcades and want to relieve the good ol' days when arcade beat'em ups were about simple button mashing mayhem. Even then, I'd advise them to wait until the price drops to about 400 points (or 5$) as it would be a much better price point at which to pick this up.
In conclusion, this game is passable. But with games like Castle Crashers which have redefined the beat'em up genre not only in looks, but in content as well, passable is just not good enough in today's videogame arena. Try again, Ubi...