Yes, Blackbeard has the same basic beliefs and qualities as Luffy, but due to his personality, they are darkened and twisted, establishing him as the perfect foil for Luffy. He is definitely the ultimate rival for the title of "Pirate King", and that's what One Piece is about. The World Government plot-lines are just there as excuses for adventures and an interesting world, and another, secondary foil to Luffy, but his primary foil IS Blackbeard. The World Government is like, halfway between Blackbeard, as the primary foil, and a secondary foil, which One Piece doesn't really have, most people are at the 1.5 mark.