This whole debate is fun, but laughable as well! Grunge (I hate that term! Anyone that thinks Soundgarden and Alice n Chains were grunge need to just admit they get all their musical knowledge from VH1) didn't kill Hair Metal (No metal about it IMO) and Nirvana didn't kill off GnR. The masses and hair metal itself killed hair metal. It got too narssisitc and over the top, generation x was becoming self-aware of themselves and the world around them (ie Gulf War, Rock the Vote), they wanted more substance than those bands where puttiing out.
Funny to say that Nirvana killed GnR when both where extremley popular at the same time and both were on the same record label. Don't forget that the time when the UYI albums came out Axl was hanging out with Blind Melon and drapped in flannel! Everyone I knew, including myself were jamming to both. GnR killed itself and Cobain killed himself in effect killing Nirvana!