The thing that accounts for Teller and Riefenstahl's longevity is the same thing that accounts for ours. That is to say, if Teller's hydrogen bomb had ever been used, none of us would have been around long enough to survive the 20th century. And if Riefenstahl's Hitler'd had his way, the same would be true. Happily, they both failed, and here we are, wondering what it's all about.
On the one hand, it's about technology. Teller's work made use of the existing physics and technology of the A-bomb to create a more powerful weapon. Riefenstahl improved film technology by making those 24 frames per second yield their potential for persuasion. Neither Teller nor Riefenstahl created anything truly original, but they uncovered the latent powers of the originals to bring them -- and us -- to the brink of extinction. The original technologies of moving pictures and quantum physics were born, like all new things, without any idea of good and evil. However, it didn't take long before they lost their innocence and were put to use by the demonic dialectic of the century just deposed.
From an intentional standpoint, there is no equivalency between them. Edward Teller's H-bomb was created as a deterrent to evil such as Hitler, though his name happened to be Stalin. Riefenstahl's work today is only used to exemplify the power of the medium of film for propaganda, not to recruit Nazis. At least, I hope so. On the other hand, the H-bomb still has the potential to annihilate us, as do neo-Nazis just waiting to be unleashed by the right movie.
The passing of Teller and Riefenstahl marks the true end of the 20th century. My guess is that Edward and Leni are together in the next world. They have eternity to work out the implications of their work.