I'm currently reading a book called "The 100 Best Beatles Songs". I know, with a title like that, it has a really high potential to be lame and cheesy, but it's actually very good. They picked the 100, of course, but for every song, they give the reasons why it was chosen, analyze both the lyrics and music, provide session information (from the original studio logs where available), give relevant quotes from the band members, George Martin, etc., and there's a section for each simply titled "Why this song is so great".
They point out all kinds of things in the song that you may or may not have noticed before, but which make it great, and man, when you add it all up, you can see why people say that they were the greatest of all time, they changed rock music forever, and things like that.
"Eleanor Rigby" is three voices (Paul, John, George) and a double string quartet. No guitars, basses, or drums.
"She's Leaving Home" has a freakin' harp!
"When I'm Sixty-Four" has two clarinets.
"Savoy Truffle" has six saxophones. Four tenor and two baritone, heavily distorted.
Why? Because that's what those songs needed, that's why.
Structural things, like songs which begin a capella with the chorus rather than a verse. People just didn't do that back then.
And of course all the studio wizardry. Laying down 23 tracks on a four-track machine by laying down three at a time, mixing them down to the fourth, then laying down three more, and repeating as necessary. Physically slowing down the tape because it turns out that the song sounds better in E-flat than E and it was too late to re-record it all. The "Abbey Road Medley" with its dozen or so short songs which all segue together perfectly.
There were so many things that The Beatles were the first to do, musically, lyrically, and technically. Things that we take for granted today. But don't make the mistake that many do; just because these things are common today does not mean that The Beatles were "nothing special". They were most definitely special. Someone had to do each of these things first, and they were the first to do all of these things.
At one point, the Top 5 songs in the Billboard Hot 100 were all Beatles songs, there were 5 more elsewhere in the charts. 10 of the top 100 songs, all by the same band. How many bands or artists today have even two songs on the charts at the same time? And if they do, one is on the way up while the other is on the way down. Sure, you can be popular and even score a Number 1 hit with no talent, but the Top 5, all five of them? No way. Their ability to craft pop songs is unrivalled. There will never be another band that totally owned the music world the way The Beatles did.