There have been a lot of incarnations this much is true. These are my opinions from worst to best. I'll leave movies alone for now.
1. Next Mutation
Total BS! Not only do they kill the Shredder in the 2nd episode, but there is no April or Casey, and they created a marysue named Venus who comes an and steals the show. This is a disgrace to all Ninja Turtles series. I can't see a single good thing about this series.
2. 1987 Series
I actually like this series a lot but really it was not too great. It is good for kids, but characters like Raphael were just blank. Raph is the rebel of the group and in this series his temper didn't exist there are many more differences, like the villains are dimwitted. April O' Neil is very dimwitted to. The slapstick fighting is cool though.
3. 2012 Nick toons series
Good character development, but what drives me up a wall, is this Donatello crush on April. Casey is too toned down for my liking, and both Casey and April are teenagers which is a little weird. The thing that really annoys me about April is how she defeats villains. I'd rather see her defeat an alien that swallows the turtles creatively than seeing it grab her and her glow then blow it up.
The only thing 4 Kids ever did right!