Since we're just talking groups, here's mine:
1) Beatles
Tied for 2nd; proper use or not, I wanted to do a semi colon
2) Temptations
2) Three Dog Night
2) Four Tops
2) Aerosmith
2) CCR
2) Grass Roots
2) Bread (that's a surprise)
2) The Who
2) Kinks
2) Dave Clark Five
2) Jackson 5 (they actually were kick ass)
Honorable mention; another semi colon...
Rolling Stones, Skynyrd, Cream, Traveling Wilburys, ELO, Moody Blues, Four Seasons.