I liked it more than I expected, and more than most other people, but yeah, it had some major, major problems, especially plot-wise. Some of the problem were obvious rotting limbs from the cuts they did to keep Sacks from being Shredder, and others were very likely there from the start.
I was pretty on-the-fence with this director, as I hated the shit out of Darkness Falls but loved Rings so much that I've seen it way more times than the movie it was made to promote. I was hoping that he'd bring the fervor and manic energy that Rings had. Then again, not everything was obviously 100% his doing in any of these three movies. A movie sees compliments shared across the entire staff with a heap on the director, and a bad movie usually pegs the director exclusively. In this case, it oddly is shared between one of the producers (Bay) and the director, with Bay getting the biggest draw. I literally have never seen a producer blamed for a movie's failings before, even previous movies Bay had produced.
That said, I don't want a reboot as some are chanting for. No story is too bad to be saved by a good sequel, and I grow ill of the amount of reboots studios love churning through. Here's what I want from a sequel:
Obviously the story has to be leaner, tighter, trimming off the fat of obviously useless parts and just keep it concise and to the point. There were many points in this film where it took an obscenely large, out-of-the-way diatribe on something that could have been succinctly brought up. And then the end result was often massively disappointing to boot.
There needs to be a reason for the Shredder/Turtles & Splinter conflict other than "they have something we want". Whether it's the unnamed Shredder from the first film or Sacks takes over or what, the story has traditionally always held that there was a reason for them to be at odds deeper than what runs through their blood. I'm pretty sure this is literally the only incarnation of Turtles that makes no mention of Hamato Yoshi - an important part of their origin.
Perhaps most importantly in this regard - characterization. Just a few days before, James Gunn made me care about a bunch of characters I either knew almost nothing about or just outright disliked. And yet these characters that I have grown up with, who I love so much still today that I run a Wiki on them and have an entire spare room with their on-the-card action figures covering the walls... I really didn't give a toss about outside of the fact that they superficially resembled the characters I've known for over 25 years at this point.
As a result of the outcry of Weeaboo Shredder, they brought in a Japanese actor to stand around and say a few lines, then voice over for the Shredder scenes. Sacks got busted down to essentially Baxter Stockman, and Baxter himself, while in the cast actually doesn't make an appearance that can be proved (a lot of people say he's standing over Dr. O'Neil's shoulder at one point, but in both the theater and the screencap I see, you can't even tell what ethnicity he is, let alone if he looks anything like K. Todd Freeman).
If the man known as Shredder in the film returns to the story, they need to make him more than just a guy who stands around a bit and look menacing. Give him a name, even if it's Oroku Nagi!
If Sacks takes the mantle, have him be more than just a milquetoast. As much as the movie itself suffered for cutting him out of the Shredder position, he was in no way believable as the badass in the armor. If his mode of combat's going to be anything more than a gun, we've got to be able to feel that it's even possible.
Who else... If Baxter and Karai are still alive, they need to have much larger roles. It's pretty sad that the half-assed 3DS game gave them more to do than the film - and Karai doesn't even appear in it! And Bernadette, too. You don't cast a massively famous comedienne and then give her nothing to do (unless you're The Little Rascals, I guess).
As for new characters... Casey's a must, but I don't know if they're (the studio) gonna want him AND Vernon tagging along in the film and you know they're bringing Vernon back. At least Jones'll pull his weight... as much as I like Will Arnett, his character was more of a means to acquire a set of wheels than anything else.
I love the crap out of Bebop and Rocksteady, but I don't know if they're right for this series. New mutants, maybe? Bring back Tokka and Rahzar? Groundchuck and Dirtbag? Usub Gerstalk and Dwayne? And on the subjects of both mutants and allies... maybe bring Leatherhead in, in some capacity?
I did like the ways the Turtles were set apart by their attire, but I feel like everyone's outfits were way too... busy. Streamline it a bit, then we're good.
This is by far the better value because Hasbro just re-released each of these figures individually with no modifications. Yes, this very same Starlord, Drax, and Rocket + Groot are $10.99 or so, each, in stores right now.
I would've probably gone for Hulk or Black Panther, if this poll was before I saw Cap 2. That movie made me actually give a toss about movie Widow for the first time (and by extension, Scarlett Johansson), so I went with B-dub.