I've always thought Nirvana was overrated... but not as overrated as GNR.
I was never a big Nirvana fan. I have Nevermind and In Utero. Havn't really picked them up in a long time. I own them because they are essential to a 90s music collection I suppose.
There is a ton of hype for both bands. Them being classified by some as overrated is inevitable.
I really prefer the Use Your Illusion albums to Appetite as far as GNR goes. Much more diverse and more on the creative side.