Well, I never want to say I have everything by Dylan, but I'm close enough.
To me, there is no contest. Dylan is easily the most influential artist and best songwriter of the last 50 years.
I honestly think his body of work is the most interesting over that time period. That is not to say that it's flawless or always great. Dylan's work, like every artist's work, has had peaks and valleys. It has had brilliance and flaws. However, taking his work as a whole, I would say he's the most important artist of the last 50 years.
I should note that Jimi Hendrix, while he was alive, considered Bob Dylan to be the world's greatest artist. That's a pretty strong endorsement from a pretty well-regarded musician.