Just came in to say Sabbath should be in the poll before Led Zeppelin ffs.
Saw The Hawk's post above and was pleased.

The Beatles and Jimi Hendrix

I think in rock music Led Zeppelin were more influential. But the Beatles have influenced every form of popular music, whether you like it or not. In this poll, I've voted for Led Zeppelin, but in general:
The Beatles>Led Zeppelin

Frank Zappa as most influential rock musician
 

One reason for this is the Freak Out! album which was the first concept record and double album of (if I remember correctly). Prior to this, there were jazz releases and there were pop releases and there were classical and country and blues releases but there was nothing quite structured like this one. This was something that would gradually come to influence late 60s and 70s rock albums across the board. The Beatles even claimed that Sgt. Pepper was them trying to have their own Freak Out!. They do look and sound similar in some ways. If you influence The Beatles you basically earned your spot.

In my opinion, all of the polled artists/bands have had a huge impact on rock, but I think influence on music and society in general is also a major factor, depending on how you read into the poll prompt. The Beatles were one of the earlier bands listed and their popularity and variety of music sparked interest across the globe. School kids started trying to start their own bands and my grandmother was among them. She said that she and her friends even had Beatles' wigs. Beatlemania was crazy among kids back then. I'm not as crazy about them as they were, but they have so many great and well-known hits that it's hard to ignore, even if the music doesn't connect or strike a chord with you personally.