The Beatles were my absolute favourite band back in high school, as well into my early college years. That was the time of my life when I was utterly obsessed with them. I made it my mission to not only collect all their albums, but all of their post-Beatle solo albums as well. I'm not as much as an active fan of them nowadays, but I still really like their music.
It's interesting to see that a few people didn't care for their later output. While I do love their early rock 'n' roll songs as well, I enjoy their drug years because it's when they really began to branch out and get creative in the studio. By the time you make it to Sgt. Pepper's, you can see how musically diverse they were becoming.
As Littlefoot fan 1990 said, I don't think I could narrow it down to just one favourite song. They have so many great ones, and sometimes it depends on my mood. But right now "Within You Without You" is stuck in my head. It might be my favourite George song, at least.