I also thought Sergeant Pepper was overrated. I think that it was the first time that their ambitions exceeded their writing ability.
"Revolver" actually has more revolutionary songs on it and the sheer energy and innovation is breathtaking even now. Play it next to a U2 album and U2 sound positively conservative. On "Revolver", The Beatles pushed the existing technology to its limits - and the songwriting was there to match. On "Pepper", they were using new sounds, but the songwriting was comparably weak. It's a thing of its time, I guess, but I can think of five or six Beatles albums, which I would rather hear than Sergeant Pepper.