I find Elvis's music has aged better than the Beatles
For the following reasons:
1) vocal ability. Now that music is autotuned, the Beatles wouldn't be able to release vocals so pitchy and often weak, if made today. So their vocals aren't up to today's standards.
Whereas Elvis, for the most part, was pitch perfect. His voice has such tonality, grit, softness, strength, range, that he is a pleasure to listen to these days just as much as in his prime.
2) Recording quality. Both the Beatles and Elvis started with very basic sound quality, but it has a classic sound. Elvis went on to enjoy the use of the best studios, live bands and orchestras. His music sounds very polished.
The Beatles went for a different direction, more experimental with their recording and production techniques. Although it may have sounded edgy in its time, now it just sounds distorted or sloppy.
Yes, I know that they wanted that sound, but it hasn't aged well. Nobody is listening to Get Back and thinking "all music should sound distorted like this!'