Both are probably the most overrated bands within Rock and weren't even the best bands of their respective eras.
I like both though but ehhh. Sixties wise I'd rather spin Velvet Underground and Rolling Stones, and Grunge wise i'd rather spin the other three good grunge bands in Soundgarden, Pearl Jam and Alice In Chains 
Nah, they're not overrated. I will say though that I think most of their albums are not as good as the sum of their work. Like for instance, before I heard Sgt Pepper I assumed that songs like "All You Need Is Love" and "Strawberry Fields" were on there. They were from around the same period with the same psychedelic style, but of course they were used for Magical Mystery tour. That's the thing, they spread a lot of songs over various projects. And that makes the sum of their work great, but would have made certain albums better if they just stuck to that.
That said I could give you some examples of why they are not overrated.
Helter Skelter. A song seen as a huge influence on Heavy Metal. Some might say the first heavy metal song. You can hear it when you think about it in those terms.
Tomorrow Never Knows. You could say one of the first electronic songs. It basically uses tape loops. Not the first bit of music to use tape loops, but certainly the first pop song. And to think this was made in the 60s and still sounds modern. Imagine ehat it sounded like back then. Must have blew people's minds. We're talking real innovation
And these are just two songs. The beatles were hugely influential, in well, music full stop.
