Personally, I find enjoyment in the music of the Beatles, probably more than I do in the music of the Rolling Stones, the Who, or the Doors. This enjoyment is not based on my opinion on whether Ringo is a better drummer than Ginger Baker, or Jim Morrison is a better lyricist than John Lennon. It is just enjoyment and doesn't need to be rational.
I suspect my enjoyment of the Beatles is largely based in a few simple facts. For one, I was exposed to the Beatles's music at a crucial time when my musical tastes were forming. I turned 10 late in 1964 and went through early adolescence listening to them. Not only are these songs blazoned in my brain from all that radio play or listening to their albums, but they are not so difficult to sing that I cannot sing most of them. And I still find them fun and evocative, which is enough to keep them fresh and enjoyable. The finer points of musicianship are irrelevant to this enjoyment. There's nothing very musically nuanced about Baby You're a Rich Man or Yellow Submarine, but they are memorable, clever singable songs, like most of the Beatles' output.
As for which, if any, of these groups will still be appreciated 50 years from now, I suspect that, much like Louis Armstrong and his Hot Five or the musicals of Rogers and Hart today, there will be a small group of fans who will treasure each of these 1960s groups and their recordings, but they'll be a tiny minority compared to the fans of whatever contemporary music is popular in 2065. The best of 1960s pop music won't be forgotten, but it will occupy a rather minor niche by then. And we'll be dead.
Probably still bored to tears by the Dead (and Phish) by then, too... I think that was from both overexposure (an older brother followed them around in his van for 10 years) and not being much into noodling/jamming of their kind. But no doubt there will still be Dead Heads around, if only as severed heads in jars, ala Futurama..!
They missed such a great decade of music in the process, too!