John Lennon for me. BY FAR. He wrote all my favourite Beatles songs and always sung my favourite beatles parts.

Note: The "best" part of "Day in the Life" is Lennon's part for me. The section McCartney wrote actually ruins the entire song for me.

Pete Best.

Juice

Technically John is my favorite, but I very much preferred them all together than any one of the them separately.

George Harrison because he wrote and sang Taxman.

Ringo, but that's because my first ever song I heard was Yellow Submarine.

George.
Most of my favorite Beatles songs, including my all time favorite (While My Guitar Gently Weeps) were written by him.
I loved the spiritual, introverted, preaching natures and and life messages of his songs, especially in his solo career. Of course, John did that too with stuff like War Is Over (If You Want It), Give Peace A Chance, and of course, Imagine. But John's songwriting in that field was more extroverted and aimed at society at large & challenging the system.
Whereas George emphasized looking within yourself, exploring your faith, beliefs, and the reality of your own mortality. My Sweet Lord, All Things Must Pass, What Is Life, and Isn't It A Pity being a few examples.

Jaime Reyes.

I should re-iterate it was the first Beatles song I ever heard, but then again, my dad told me that was when I was like one or two so it was probably one of the first