With an artist like Bob Dylan, he has so many albums that it's hard to say one album is the one. Strong arguments can be made for one studio album over another. A good sampling is his Greatest Hits album released in 1967. I've included a link to his discography, and as you can see, some of his best work is on this record: Blowin' in the Wind, Rainy Day Women, It Ain't Me Babe, etc.

I also like Blonde On Blonde, Highway 61 Revisited, and Blood on the Tracks. He did a great song (not sure which one of his albums) that was featured on The Soprano's Soundtrack Vol 1 called You Gotta Serve Somebody.