Ah, dear Eric! At last we disagree on something!
Y'see, you have to take into account the era those movies were made in (and Superman II was mostly material done for Superman I that had to be cut out and made into its own movie... sorta like Kill Bill).
The pinnacle of special effects was Star Wars (check out the non-Special Edition version of Luke's landspeeder and the 'blot' beneath it). Before Superman I, the last person to fly on screen was - what - the Flying Nun? Those scenes of Superman flying to catch the helicopter, or his flight-and-smile in the upper atmosphere were jaw-dropping!
The cheesy aspect was all over the comics since the Batman TV series. Comics were very tongue-in-cheek, with nearly every Superman comic ending with him blinking at the reader like they share a common secret.
Margot Kidder is the weakest link to me, I agree on that. But Luthor was his usual Silver Age self.
Back in the day, Superman had, among other things, a superkiss that could erase Lois' memory if he wanted -- darn good at tonsil hockey, those Kryptonians, eh?
Ditto for the spinning back the Earth to reverse time gimmick. Sounds like a valid Silver Age plan, and something the Silver Age Superman would be able to do.
All told, those movies would be average (say, a '6' for me) if not for Christopher Reeve, though. He embodied the character so thoroughly that his mere presence (as Superman or Clark Kent) elevates those movies to '8's. Of course, his presence assures that Superman III and IV even get rated, otherwise they'd ooze down the drain into the netherland that entraps movies such as 'Captain America' (with the italian Red Skull) and the Romero 'Fantastic Four' movie.
Plus, how can you beat 'KNEEL BEFORE ZOD!'?