Four chords that made a million

 

E Major, B Major, C# Minor, A Major.

 

All the good Country songs (yes, this may be oxymoronic) also use the same four, with one minor variation:

 

E Major, B Major, F# Minor, A Major.

 

Funny substituting F# Minor for C# Minor makes the song appropriate for being drunk at a roadhouse.  See Gary Stewart's She's Acting Single (And I'm Drinking Doubles).

 

Of course the four may be mixed and matched with regard to sequence.

 

As for the blues, yes, generally three chords.  But ya really need to listen to some Lightnin' Hopkins who could twist those three and play a frankly weird version of the standard 12-bar blues, where some bars were 11 and others 13 and others just who knows what (q.v. Captain Beefheart).