I, too, remember well the Cryin' Shames and Shadows of Knight. Actually heard their version of 'Gloria' far more often back then than Them (Van Morrison, who wrote it). My "music mind" in the 60s was filled with James Brown (who rarely made it into the top 20), Hendrix (I don't think Purple Haze or Foxy Lady made it into the top 20), The Underdogs, The Rationals, etc. I think a one hit wonder is that song which most people will remember 10-40 yrs later. Everyone who had a hit did more songs which, just by name recognition alone, would make it into the top 100. They usually died on the vine quite quickly and I don't think these qualify for second or third hits.
? and the Mysterians are a perfect example as are The Looking Glass which had a hit in 1972 with 'Brandy (You're a Fine Girl)'. And let's not forget my boys from here in Detroit, The Amboy Dukes - 'Journey to the Center of Your Mind'. What a great song!!