loner dude the problem is that no matter what those bands will do or done till now, it was probably done better in the 70's... the only good thing i can say about today guitarists is that they are probably techniqualy more skilled then the 70's people, but then again ritchie blackmore for example was fast, and had a great feel. today players tend to be only fast, and u are talking about those bands not getting into mainstream, this is true there are alot of good players that are not mainstream, but then again think of the thousands of local players or guitar teachers around the world, who can kick any pro player's ass, offcorse you dont know them all, and probably big part of them could be the best players ever and everything, but we are not talking about all those people, and believe me in the 70's there were also a lot of bands, that were great but didnt hit the mainstream...
and i dont think that a mainstream is a bad thing, i think that all the styles in the world have their own mainstream, and being mainstream band, is not being pop comercialized band, for example check out the zeppelin records: they have sold the second biggest ammount of albums in the states, and yet they are not comercialized band, but rather a band that almost every single man likes, because they wrote a great music