Or are there any? I'm trying to figure out which to run. I see that 3rd and 4th are pretty different, but could someone give me a run down on 1st/2nd?
Certainly long winded and does not detail rules changes as such but Gamma World: Over 30 years of I have no idea what is going on. covers the evolution of the game. It should give you the differences in feel between the two editions.