I voted for Superman I. I saw it many times over the years, but it wasn't until I was an adult that I started to notice all the nuances in it. for example when Clark is running to catch an elevator and says "Going down?' The guy in the elevator sticks his hand out and says "No! up, UP!" As a kid I thought, "what a rude guy." As an adult I realized "Ahh, allusion."
I kinda like the way he turned back time. Yeah, it isn't in his portfolio, and it doesn't make a lot of scientific sense, but it was an emotionally powerful scene for the Man of Steel.
The second movie always seemed a little too contrived for my taste.