Luckily, it seems like they are all being undone for the 50th next year. Most of them, anyway. We'll have to wait to see the release to be sure, but it's a definite improvement. Maybe the definitive version, finally.

I was talking to Bob Gale once about this topic and he said that him and Zemeckis had put a veto clause in their contract when they sold BTTF to Universal in the 90s giving them the power over any later fuckery with the releases, while they are alive. This was during the height of the 3D TV craze and he said Universal had asked for permission to do a 2D->3D conversion of BTTF and both Bobs had refused. So there's one franchise at least that won't get dicked with in the near future.

[I'm not totally against 2D->3D conversions if done right. The Titanic conversion looks like it was filmed 3D-native, beautifully done. The Star Wars: Episode 1 conversion is essentially unwatchable and killed the whole project.]