Josh Barnett - Debatable. While he's always been a top HW, he's never had a point where you pointed at him where you thought "There goes the best HW in the world." His UFC run was marred by controversy, in PRIDE he was always behind guys like Nog, Fedor and CroCop and completely blew his chance at making his mark when he pissed hot at Affliction.
Rich Franklin - UFC Hall of Fame for being the ultimate company guy, not MMA HOF? Nope.
Shinya Aoki - Say what you will about him being one-dimensional, but you have to throw him in. He's had amazing run against top talent in their primes that if any other fighter had, he'd be a shoe-in and arguable LW GOAT. He's beaten Uno, Hansen, Shaolin, Alvarez, Kawajiri, Rumina Sato, and Kitaoka. Just because he lost to Gilbert Melendez (who is an elite fighter in his own right) in his stateside debut doesn't override all the other accolades,
Alistair Overeem - Nope. Very talented, but underachieved* at 205 and most of his accolades are K-1. He needs to have a quality UFC title reign to be considered.
Frank Mir -LOLNO. Next question.
Gomi - Abso-fucking-lutely. LW GOAT. Dominated the LW scene when all the top talent was in Japan. Yes, he's fallen off, but to leave him out would be a sham.
Tatsuya Kawajiri should be at least be a ballot finalist. The guy has been a LW top dog since 2003 and was still Top 10 last year before he made the jump to featherweight. It hurts that's he's never had his time in the spotlight as the #1 guy post-Shooto, but that kind of high-level longevity is almost unheard of and he's only lost to the best of the best (Alvarez, Gilbert, Aoki, Gomi and Shaolin).