This isn't going to be easy...

1. "Abbey Road" The Beatles
2. "The Times they are A-Changin" Bob Dylan
3. "Sgt. Pepper" The Beatles
4. "Birth of the Cool" Miles Davis
5. "Led Zeppelin IV" Led Zeppelin
6. "Nevermind the Bollocks, Here's The Sex Pistols" The Sex Pistols
7. "Best of Bowie" David Bowie
8. "OK Computer" Radiohead
9. "My Aim is True" Elvis Costello
10. "40 Licks" Rolling Stones

And that's only scratching the surface

Though I am probably biased, I would say that the musician who has had the greatest impact is Bob Dylan.  Not only did he help revive rock and roll music in the late '50s, but almost every other significant artist of that time lists him as a prime influence in their song writing.  The Beatles have openly admitted that after meeting Mr. Zimmerman they were greatly inspired to make their lyrics deeper and give them more significant meaning (not to mention the fact that Bob introduced them to hallucinogens which I would argue to be another prime influence in their transformation).  Dylan has also greatly impacted the way that mainstream literature views song lyrics.  His writing is honestly some of the best poetry I've ever read.  He blurs the line between bard and popstar.  

A true story in letter form:

Dear Mr. "I drive a white pontiac Vibe",

You cut me off at the four-way stop.
Your car isn't that great.
Stop being a pretentious asshole.
You're a dick.

Love,
Me.