Seventh Son gets my vote.
Of course you can't go wrong with picking anything between '82-'88 with Maiden since that five album run is just about the best in metal history.
What they've released since Bruce got back with them has been equally impressive as well.
I was thinking about creating a poll like this with one of the more universally loved bands on here like Maiden or Megadeth. It makes for a better discussion if a poll can get the majority of everyone to chime in on it unlike the CC and Death polls.