I agree that they may not have been the best musicians, Cobain wasn't the greatest guitarest and singer, but to me that's the whole point.
How can someone like that have such a huge impact and influence then..??
Feels like Teen Spirit just totally summed up an entire generation, niche, genre - whatever you want to call it. That one song can be related to by just so many people.
The way Cobain stayed away from 'image' and 'safe' side of music, like mentioned before in this thread, once a band has got a fan base / image or have created something for themselves, they then play it safe or sometimes go commercial or follow the fashion / trend of the time to stay in the charts or public eye.
Cobain had such a huge fan base, but he didn't want any of the above - to me, I give him alot of respect for that.
Also, finally, MTV's unplugged - a band like Nirvana who's sound is quite 'heavy', to pull of something like MTV unplugged in a way that was so 'soft' yet it was still such a powerful perfomance, for me (and in 1991 I was a full on 'raver') Nirvana definately are one of the greatest.
Here for such a short time, remembered by so many for so long, never to be forgotten - enough said.