Dwight refers to Michael as "the one person I have been hired to protect." Because of his authoritative personality, Dwight worships his boss. He sees Michael as a means to an end, and thus bends over backward trying to please him. Dwight is always the first to jump in on Michael's hare-brained schemes but to the contrary of his ideas isn't really the number one in Micheal's eyes (Jim Halpert and Ryan Howard seem to come before him).
As well as shown in an earlier episode in the series (The Coup) Dwight really doesn't like Micheal as much as he appears to. This is shown after Dwight is tricked into thinking he became the Regional Manager and exposes some truths about their relationship.
Michael finds Dwight irritating, but enjoys the attention and devotion Dwight lavishes upon him.