Never played the originals.
IMO Fallout: New Vegas is the best, followed by Fallout 3 and then there's Fallout 4.
76 is probably the worst, although I haven't played it.

New Vegas was the only game where I felt full 100% freedom.

I think Skyrim sucks, even worse than Fallout 4 and Todd Howard is full of shit :P

*As long as they don't take their game development seriously every forthcoming release will suck and repeat the old formula. I'll get interested in this series again once they get a new game engine. They've been using the same old engine since Morrowind.