I had to think so much before answering question and I am still not clear, probably, the reason you will find my answer ambiguous. Let's start with something - Nirvana - Grunge existed before Nirvana but they made it famous, 3 albums, that's all. read more
Nirvana probably would have altered their grunge sound somewhat to me more inaccessible and more hardcore punk and noise-rock influenced (or gone more acoustic) but I think Radiohead would have been the more acclaimed band if not the more commercially successful. read more