Who owns the rights to popular 1980's cartoons that haven't gotten a modern live action movie?

Because I personally believe American tv has taken a downturn, I have taken it upon myself to present the younger members of my family with the nostalgia-fest of both 80's and 90's cartoons, so I worry about what they will be exposed to in later years in cinema.

Say what you like about Micheal Bay's Transformers and TMNT, they are going to have sequels possibly into the 2020's and many studios will follow this trend.

So I'm asking: who owns the rights to, and will be responsible for making, movies concerning popular sci-fi & fantasy cartoons? ( like He- Man, Thundercats, other )