I'd say probably Tonal or Spider probably. Though Jameson Connemara is making a strong case if he can keep up the pace he's on.
I didn't even think about Connemara. But now that you mention it, nice wild card. He is very good. I think he needs to go to EVO and Syn and destroy the 145 and 135 divisions. That would cement him as a serious contender for the GOAT. Considering Charles Martel is 45, Jameson definitely has time to. While we're on the subject of current fighters, a third fight between Spider and Ferreira, (which I think should and will happen at EVO 200), would put the winner in serious contention for GOAT as well. If Colin Croft can keep up his pace and become the first fighter to finish with an undefeated record, that would basically leave no question for GOAT. YB Sol in his early days, before he just decided to Tito Ortiz, is one of the most underrated fighters ever. He should be in the HoF.