Like what was said with 'Teen Titans: The Judas Contract' (which to me was the better film), 'Justice League vs. Teen Titans' may not be among the best of the numerous animated superhero/comic book films, and there are some pretty good to excellent ones out there (as well as some disappointments). Can definitely see why it's divided fans and it's towards the weaker end of the films, but there is a lot to like here.
It is not in the same league as the animated 'Justice League' show, the 2003 'Teen Titans' or 'Young Justice', all three wonderful shows and three great examples of how to do iconic superheroes justice. It's certainly far more preferable than the series 'Teen Titans Go!', that was cheap, poorly written and was basically dumbed down childish stupidity that forgot basically everything that made the original series so great.
There are some not so good points with 'Justice League vs. Teen Titans'. The romantic/love interest subplot was forced and unneeded. The expected big fight indicated in the film's title was too short and anti-climactic.
Not all the characters are particularly well handled. For examples, Trigon is far too ordinary a villain with very little to him and he is poorly utilised, Raven didn't seem developed enough and wasn't compelling enough for a character so heavily focused on and the whole Beast Boy's forms stuff was interesting on paper but was very confused and underdeveloped in the film. Taissa Farmiga sounds like she was phoning in as Raven. A longer length may have helped.
However, there is a good deal to like about 'Justice League vs. Teen Titans'. The animation consists of atmospheric colours, detailed character designs and backgrounds and fluidity of movement. The music has an ideal mix of haunting intensity and jaunty infectiousness.
Really liked the dark grit tone the writing, while adding a little levity here and there to stop it from getting too seriously. The story may be standard and doesn't break new ground, but it's fun and absorbing and goes at a snappy enough pace. The action is thrilling and generally the characters and the interaction intrigues enough. The voice acting on the whole is well done.
Overall, decent but could have been a lot more. 6/10 Bethany Cox