Being a big name is not sort of the point with Bond. Connery, Lazenby, Dalton and Craig were hardly box office names when they got the gig. The very fact he is not wholly on the radar puts Cavill in better stead than most and just because he is not known to the man on the street does not mean that industry circles are unaware of him.
I agree, BUT all that buzz he had five years ago doesn't seem to have been parlayed into very much. Other actors who were relative nobodies when they auditioned for CR have gone up in stock since (Sam Worthington, Matthew Goode, etc), but Cavill seems to be in the exact same place he was in 05. If he is this alleged great undiscovered talent then you'd think he might have broken through by now...