I am 61, and have been listening to "rock" or "pop" or "alternative" for 50 years.  I still buy music, and have seen the Cure, Arcade Fire and Radiohead live over the past few years.  Needless to say, I have given this a lot of thought.  My answer follows.

 In a class by themselves, and roughly equal in my opinion, are the three already named.  Each of them, in their turn, brought into existence a whole new sub-genre of our music.  (It is a measure of AF's greatness, in my opinion, that I can include them after two albums.)

 Following the "big three", in rough chronological order, are:  a) the Doors; b) Pink Floyd; c) Roxy Music; d) the Clash; e) Joy Division; f) Ride; g) Placebo; and h) Interpol.

And yes, I know there are 11 named. 

hmmm...

1. Beatles
2. Lynyrd Skynyrd
3. Guns and Roses
4. Iron Maiden
5. Steve Miller
6. Led Zepplin
7. Nirvana
8. CCR
9. Blue Oyster Cult
10. Stevie Ray Vaughnn