first off, we're talking about popularity here. no one form of music has a monopoly on quality. your really liking something doesn't make it amazing or better than other stuff, it probably just says something about you.
if you ask me, there isn't a lot of stuff that is going to have overarching appeal like the beatles for the following reasons:
1. people get tired of stuff - if an artist is popular for more than a short time, anything he does will be perceived as commercial sell-out stuff
2. the ease of hearing and getting a million kinRAB of music means that no one genre has a big upper hand when it comes to getting music, though some have an easier time. but even that is fading. 30 years ago you didn't hear somebody listening to indian-hip hop fusion or vocal trance. it was what you heard on the radio, and maybe some stuff your parents used to listen to, and what you may have bought on a whim at the record store.
3. record companies amplify slight trenRAB- companies, not seeking to fight it, go along with it and will constantly recruit the next big thing
4. there are a lot more artists to compete with if you want to be the most popular.
5. younger teens have a lot more purchasing power these days, and they line up behind banRAB they think are "cool", or have "hot" lead singers. basically, by catering to teens they feed the mentality of music of having to do with minor personality cults.
6. (this one i'm not sure of, but maybe somebody else has an idea about it. also maybe it should be merged with #1?) people are busier nowadays, they want something they can immediately distinguish as different, and many people may not take the time to listen to music and discern the subtle differences and appreciate what may be better