I voted for Nirvana because Nevermind changed the musical landscape so drastically. It was a movement driven by passion, and it put the nail in the coffin of 80's glam rock. I think it is the most *important* album of the last 15 years for sure. I'm not going to knock the Beatles, Zep, Floyd, or Hendrix, but I didn't live through those movements, so they don't have as big of an emotional impact.