I'm pretty sure that if it wasn't for the Beatles mostly, and a handful of other groups at the time, we would not have seen the HUNDREDS of great bands that emerged in the late sixties and 70's. IMHO, other than great music, it was what they help start that is their legacy. They were inspirational (with a few others) to teh movement. Look at what lack of inspiration causes, right now there is a dearth of good musicians and good bands. If you don't believe me, name the top music albums as awarded by the Grammy's for the past 10-20 years - what are these bands doing today?
I would say that there is a dearth of good musicians and good bands that get radio playtime or that can be heard outside of independent labels and samples from the internet, but I think there are a lot of great musicians out there who can't make a living and that we never hear. The industry has become entirely managed and creativity that falls outside their marketing scheme just doesn't see the light of day.