It was 44 years ago that...

Maybe not to the extent of Sgt.Pepper's but:

Elton John-Goodbye Yellow Brick Road...proved you could sell millions of copies of a double album.

Peter Frampton-Frampton Comes Alive...proved you could sell millions of copies of a "live" album.

Pink Floyd - DSOM - Made a BIG impact

Moody Blues "Days of Future Past" first concept album?
Also right about the same time as Sargent Pepper's

Nirvana - Nevermind
Led Zeppelin - Led Zeppelin

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Many great albums that influenced other artists and the direction of music have come out, but I can't remember any one of them having the impact of Sgt. Pepper. I remember when it came out. Even if you didn't sit around and listen to it, it was everywhere and you knew all the words to all the songs, it was that ubiquitous. It came out the windows and doors, in the hallways, in the car, everywhere you went.
I was more a Stones fan (you were either a Stones fan or a Beatle fan), but Sgt. Pepper was the s**t! Sgt. Pepper changed the course of pop music then and forever. It was a singularity that no record has achieved before or since.