Eric Carr (KISS), and Phil Lynott (Thin Lizzy). Forgot his name but the former lead singer of Boston, Dimebag Darrell, Layne Staley, the REAL Guns N' Roses lineup, Chuck Schuldiner, Randy Rhoads, Freddie Mercury, Bon Scott (Those two, being the best hard rock singers of all time in my book), and SRV of course.
As far as Cobain's Muscianship goes, he was just mediocre at best, never could compare to the diversity of Staley and Vedder's voices, or Cantrell's guitar playing. All I remember Cobain for, is banging on power chords, playing simple riffs and screaming vocals. Don't get be wrong, he is missed, but he is way way over rated and cliched. And as far as Frank Sinatra goes, he was very old when he died, but still a great singer.