I think the choice is impossible. Of course his seven first albums (til' Blonde on Blonde), the next one (John Wesley Harding), but you absolutely need the two last (Time out of mind, Love & Theft), some in beetween (Nashville Skyline, Blood on the tracks)and the Bootleg Series and Biograph... It should be comlete.

Serioulsy, reduce to five, I would choose albums from the 60's first, but what he made in the ten last years(from Good as I been to you yo Love & Theft, including participations to various tributes and soundtrack) is amazing and is close in quality to his first years. It should not be overlook.

SP