I love this song unquestionably. The case for it as the best pop/rock song of all time rests on its perfect realization of its purpose. Sure, the Beatles later developed into revolutionary artists, but in 1964, they were hitmen, trying to keep their career at its height, and to do that they just needed to make sure they topped themselves and never faltered from the main principles of pop songwriting. Pretty easy, right? Don't answer that.
But it so perfectly captures that Beatles enthusiasm I remarked about in my write-up of "She Loves You," that simple yearning desire for contact. It's not that they genuinely believe hand-holding is the apex of expression for a relationship, it's that when you're a kid, and you don't know better, that desire is so loaded you don't know how to express it. So when a song like this comes along and gives it a voice and a form: "I wanna hold your HAAAAAAAAND!" it just clicks! It does, moreso than "Please Please Me" or "She Loves You," great songs as they are. This one manages to hone in on a moment, a motion, a feeling, a position that is very real and tangible, and yet so impossible to describe. That's what music is for, especially pop music. It isn't there to outsmart its audience, or bring them higher. It's just there to sit next to them and nod along. It's there to hold their hand, and all that that implies.
See what I did there?
The oft-repeated line about The Beatles is that they "invented" the idea of the "rock band." In the past it was Elvis and the Blue Moon Boys, Buddy Holly and the Crickets, Bill Haley and his Comets. Pros whose job it was to make the frontman look good. But there was no frontman for the Beatles, there was four guys who all had to shine all the time. Everything on this song is a testament to that. The guitars are living things bouncing off each other, the bass weaving between them. A classic dual-lead from Lennon and McCartney emphasizes the song's soft-loud dynamic, jittery in the verse, gradually building confidence for the excited chorus, and dreamy and wistful in the middle eight. It's everything a pop song can be. Ringo even pounds those drums with extra zeal under that first scream of the title phrase. Everything about this song is put in place for a purpose, there's no background. Right from that opening riff, which puts the listener on alert that this is something new, this song is practically an opera.