Most prolific could be Frank Zappa who released loads of album in his lifetime and apparently left a large body of unreleased work in the studio also....as for least perhaps the stone roses could take that title.....it took them seven years to make a follow up album to their debut and then they all seemed to decide they couldn't be ar5ed to keep going.
Kraftwerk could be the least prolific - in the last sixteen years they've released one new single and an album of remixes. And Enya's 17-year solo career has produced less than five hours of released material.
Guns and Roses (or Axl Rose and whom ever he feels like recording with today) are getting there - eight years and counting waiting for their 'new' album ...
agree with sft42 re most prolific but least prolific award must surely go to Kevin Shields, who has yet to release a My Bloody Valentine follow up to Loveless from 1991