What is the best Beatles Song ever?

I threw a couple of Beatles parties at the library I worked at.  At one of the parties, my guest speaker was a professor of music who talked about how really very good the Beatles were at song composition.  He cited "A Day in the Life" and "She's Leaving Home" as examples of excellence.

Where do you start? It's a great body of work. Almost sacreligious to pick 2 or 3.

I mostly like the ones with the least overdubs, where they play as pure rock 

quartet. 1.) Back in the USSR-just two guitars, harmony vocals, punchy rhythm section  

work by Paul/bass, Ringo/drums.

2.) Helter Skelter-for basically the same reasons.

I suggest you all get a copy of The Beatles Naked. No strings or fills. Just them.

I think their whole catalog is utterly fabulous, I could have any of them. I just happen

to like these two for that reason.

Too many great songs to choose only one. Dear Prudence, I am the Walrus, Baby Your a Rich Man and all the takes of Strawberry Fields Forever come to mind. Usually whatever I’m listening to is my favorite. A Day In The Life is probably the song I listen to most often. 

"Let It Be"--such a sincere, prayerful and comforting song

Here, There And Everywhere    (one of their finest love songs)