While most bands play in only just one genre, the Beatles were all over the place. They played pop, rock, psychedelic, folk, blues, hard rock. they kept changing and introducing new things, that was never done before, on every album they release. They did all that without losing their fan base and everybody was trying to copy them.
that is why they are the greatest band of all time. :)
This is a part of my Tribute to Beatles Project.
Hope you like it.