this is going to sound harsh but - nirvana wouldn't be held to such a high standard if cobain was still alive. it takes more to carry on in the music business than to become the "beloved" martyr.
That's debatable. I'm curious what would have happened though. There wouldn't have been a Foo Fighters. I think that if he were still alive, they would have split at one point, then got back together for a HUGE reunion.
But back to your original point, I think he still would have been held in a high regard as the man who ushered in the era of grunge. You can't that away from him and his band. I'm curious where they would have gone musically.