Anyone who thinks the Beatles are overrated is wrong.
They single-handedly revolutionized not only music, but what people wore, how people thought...
Nowadays a band puts out one good album and then rides on it for the rest of their career. In three years (1966 to 1969) they put out Rubber Soul, Revolver, Sgt. Pepper, The White Album and Abbey Road. Most artists would give their left nut to put out even one album that good.
However at they beginning they did cover their fare share of Motown songs/Early American rock tunes and standards.