What do you think about the original Donner Superman movies?

This is a big gap in my film knowledge as I’ve never seen them. With all the hype about Gunn’s version, I thought of giving them a chance.

I see they were shot at the same time, but 3/4 of part 2 done, Donner got fired and a new director came back and reshot 2 almost completely? But then Donner restored his version decades after but it was inevitably incomplete and had to Frankenstein bits and pieces from the other one? Which version of 2 should I watch?