So whats so great about Grunge music?

Music changed and grunged bands wiped out hair metal bands. I hear Nirvana about 2009 and I thought they were bland, I thought Nirvana was overrated because I didn't like the sound. This year, I started to hear more Nirvana, and I relized the sound was different and it sounded better then the crap I was hearing. idk, how to explain, but I love Nirvana now it's one of my favorite bands. Nirvana did lead the way for crappier bands, but Nirvana wasn't crappy at all. And duh, grunge is alternative and modern, maybe it's your taste. It was something new and all the 90's teens got into it. They were the most original alternative band, that's why they're great, Kurt Cobain is a awesome guy, to bad they only made 3 albums.