I often wonder, with what degree Sgt Peppers can be fully credited as being the Ultimate Album of all time (a title which is often embraced throughout the numerous 'greatest Album Polls') Although its a revolution in its own sense (when looking at elements such as design, marketing and effort), the context of the Album is not so sharp.
I think the Sixies feel of Sgt Pepper is a little tiresome, sadly spoiled by the 'colourful commercial parody' that plagues today's compilations and films etc
For me personally, I think other Beatles albums give a 'better' Sixties feel. Not so much better, but more realistic, gritty and exciting. Hard Days Night I feel gives a perception of real working class, with the monochromatic colour scheme as emphasis upon the basic ideals which stem from the Beatles attitude and roots (a sense which obviously does not exsist in the same format)
If we are talking about the 'psychedelic' period of the Sixties, for me, Magical Mystery Tour really unearths the naive, experimental and often dark sense of nature from which Acid-Inspired Idealism spawned from. This can also be attributed to Yellow Submarine (film) in which the Colourful revolution is mixed by bleak and dark animation and glued together by theories which can only be described as puerile.
Sgt Peppers is one of its kind, but I often see it as an album that was saturated by ego,  given to the people by establishment-crushing demand, and thus manipulating its form into more of a faked state* (Lennon remarking on the cop-out like concept)
The Songs are all great..with one of my favourites (and many others)..A Day in the Life...but its the meaning of Peppers I feel is often mis-interpreted..an Album used with cringing-ease to 'sum up the Sixites'.

Im guessing almost definately

Unfortunately it's like telling someone about the war but not really being there! The impact that this lp had in 1967 was staggering! Everyone was trying to dissect each song on it! Months before its release the British press had stated that the Beatles had run out of steam! They of course proved them "very wrong"! It was reffred to as "POP-ART" The cover was discussed over and over! It became the anthem of every flower child the summer of 67! If you listen to it on headphones you can here the vocals in one ear and the music in the other! Paul's basslines are almost overpowering on some songs! This lp should be intoduced as the day pop music was validadted as a reconnized form of music! I could go on forever but I won't! I will just leave you with a poll from Rolling Stone by 17 music jouranists who had to lay out the top 100 lps 1967-1987! Sgt. Pepper was voted #1 because of it's importance in the music world! Overrated not likely. Talked about forever most definately!

i dont think its over rated at all

Pepper isn't overrated...it's strictly a matter of opinion, however Pepper did the most to influence the industry so that's why people identify it as being the Beatles' best.

My son just recently took Sgt. Pepper repreise song and added some perfect time suffle beats and gave the boys a echo wave reverb on their voices which made the song sound totally cool! He played it for his music teacher and the guy freaked out! It came to me that the program and computer that he was using was probebly more complex than the original system used to make the lp! His program was "acid-pro" and he could map out the song on this computer and add beats at the exact moments to splice them together! Off topic he took the I"m a Babie girl and spliced them in 8 different langues to make one perfect song! To think I was just happy to put on an lp at his age!

Pepper isnt overrated, at the time, nothing sounded like it, and it was weird and something diffrent, and it made people think of music as an art

But the feeling was in the air, and influencing many other bands... Cream, Hendrix..just to stay in the commerical realm.
Im not digging Peppers...cos I love it..But you cant just say that the Beatles were making music in this way.. its just they done it the best.