Cobaine definitely had a very influential impact. His music was where rock made a return to a more raw and unrefined sound. Grunge was a kind of music that came to embody people who weren't necessarily cool and it was really all about music that was much less refined (than say Britney Speares), but had a lot more depth and emotion to it (than Britney Speares.) Pearl Jam are another good example where rock music went closer to the music of the 60's an 70's. This music also had a lot more to say, and spoke more directly to people because most kids aren't glamorous, and the music never tried to be glamorous either (unlike Britney Speares.) I guess it can be simply stated that grunge returned rock to the core.