Allen Ginsburg, upon hearing Dylan in 1962, was reduced to tears. He said he knew the torch had been passed from his generation to the next. Dylan single-handedly changed the world, not least of all by transforming John Lennon, who pre-Dylan was merely a Pop songwriter. Without Dylan showing him what was possible, John would not have become the writer he did (for better or worse ;-). He also introduced John and the other Beatles to Jazz cigarettes!
Dylan has had many "periods" (as they call them in the world of painting), changing styles without warning. The difference between 1966’s Blonde On Blonde and it’s 1968 follow-up John Wesley Harding (one of his most personal, with a lot of religious imagery) is absolutely staggering---it’s hard to believe they came from the same person. Both are amongst his best, but completely---and I mean completely---different from one another. On Blonde on Blonde he is wound tighter than a drum core snare drum head, sparks flying off him (he was pretty amped up on amphetamines in ’65-6), his Strat cranked up and running down the road at about ninety miles a hour, the rate at which the surrealistic lyrics are flying by. He has a pretty big band, with multiple electric guitars, piano, and organ. On JWH he is playing an acoustic Martin, about as relaxed as you can imagine, singing what sounds like theology discussions in a seminary. Really heady stuff, far, far beyond what anyone else had ever done, to this day, in Pop music.
Always over-looked is his "Born Again" period, during which he produced three solid albums, all having a Southern Gospel feel. Really good music, but the Christian lyrics are off-putting to atheists, which his traditional audience---the counter-culture baby boomers---mostly are. It was funny to watch their reaction to him becoming a "Jew For Jesus"!
His 1974 Before The Flood live double album with The Band, his best collaborators, is a good place to get a lot of great Dylan songs, played and sung with a lot of energy---Dylan absolutely spits out the words. It was recorded on his first tour since 1966, on which The Hawks (who became The Band upon the release of their 1968 debut album Music From Big Pink) were his, heh, band. The studio album they did together around the time of the live album, Planet Waves, is an overlooked little gem, a personal favorite of mine. It has recently been released on vinyl and SACD by Mobile Fidelity in great sound.
All his albums from Time Out Of Mind (1998’s Grammy Album of the year) forward are really good imo, having a number of hypnotically-entrancing songs ("Not Dark Yet" is a masterpiece) I can’t get enough of. You get sucked into the world Dylan creates, temporarily leaving your body and losing sense of time. Not many other "Pop" songwriters are capable of that, unlike Classical composers, who routinely do it.
Absolutely and by a wide margin the most significant, influential, "important" artist of the 20th Century---bar none, even for those who don’t particularly like him. It’s inconceivable what Pop music would now sound like had Dylan not been born. He alone changed Rock ’n’ Roll from teenage music to adult art. Some hard-core 1950’s Rockers I know wish he hadn’t!