Something prompted me to go back and watch the first two installments of Christopher Reeve’s “Superman” movies over the weekend. The first film is fondly remembered by critics, and while I enjoy it still, I could never quite explain its enduring quality. On the other hand, its sequel, which held together so well for me when I was in grade school, is a lazy disaster.

I’ve always had a hard time understanding why, even today, watching “Superman: The Movie” gives me that same thrilling jolt that I experienced when I was a kid. Its storytelling is all over the map, and it flouts so many rules that more commonly praised films adhere to: it squeezes at least three movies into one, it changes its tone and cast markedly over the course of its 02:23 running time, and it resolves itself with a deus ex machina of overwhelmingly cornball convenience.

Yet there’s something undeniable about its overabundance of heart. If nothing else, director Richard Donner infused his film with a tremendous care and respect for its source material, and the result is contagious. Every performance is heartfelt, genuine and, in the cases of Gene Hackman and Ned Beatty, comically brilliant. Scene after scene is bursting with an uncomplicated wonder, from the farm fields of Kansas to the skyscrapers of Metropolis (a barely-disguised New York, teeming with pre-Giuliani life).

The biggest wonder of all is Christopher Reeve, who inhabits the title role perfectly, turning in a performance so genial that it gives real credence to the absurd notion of a superhero. In the DVD extras the filmmakers say that the best special effect at their disposal was Reeve himself, and it’s easy to see how true this is — the absolute conviction of his performance really makes it conceivable that a man can fly.

After watching “Superman II” I understood a little more about what made the first installment so compelling: it was able to preoccupy itself with telling its hero’s engrossing origin tale. Even twenty-five years ago, the narrative from Krypton to Metropolis was already so ingrained into the American psyche that it almost surely couldn’t miss, and Richard Donner wisely spent most of energy exploring its rich potential.

“Superman II,” didn’t have this luxury. Its director, Richard Lester, was left to cope with scraps of the sequel filmed by Donner before the producers fired him, as well as Mario Puzo’s dead-on-arrival story, full of gaping plot holes and bizarre alterations in Superman’s powers. Like an exercise in sequel disasters, the movie feeds not on the epic ambitions of its source material as its predecessor did, but rather on the afterglow of that movie’s success. Nearly every moment in “II” rests on the laurels of Donner’s hard work, and as a result the final movie is flaccid, unformed and tedious.

Though Donner and Reeve’s “Superman” will probably remain the definitive cinematic version of the superhero for me, I’m not at all discouraged by talk of reviving the franchise. In fact, the idea is very attractive to me, because I think it’s the flexibility of this myth that is so appealing. Its ability to be reinvented and in fairly rapid succession — witness “Lois & Clark,” and “Smallville” — is only a testament to its power. Donner and Reeve’s version, in spite of all its wonder and how dear it is to me, is but one interpretation. I hope there are many more.