Both, easily, belong in the Canon. Which ever loses will probably be the strongest competitor for redemption. However, I can imagine Boogie Nights being done with a different director/different actors. I would still be interested in seeing a Scorsese/DiCaprio, or Soderbergh/Tatum version of Boogie Nights. I really can't imagine There Will Be Blood without PTA, Day-Lewis and Paul Dano. In my mind it is nearly a "perfect film" in so much as I can't imagine anything changing in it, and the film being better as a result.