That list of greatest captains Saru looked at was incomplete. The top entry for Captain Robau burns with such intensity and awesome bright light that it was outside of Saru's range of vision. Looking at Robau's name for too long has been known to break lesser (i.e. everyone) starfleet officer's careers from a sense of unworthiness and lowered self esteem.My assumption is that Archer didn't pick up the tagline of "Greatest Explorer", till after he brought the NX-01 back mostly in one piece at the end of his tenure as Captain.
We only hear that kinda thing from Daniels during the show and he's from the future anyway.