Arnold by far, no one even comes close,he could have won it from 70-83 no problem had he not ventured into bigger and better things, imagine a 14 year reign as Mr. Olympia,lol, oh how many sandows did Mental get
Had Mentzer not gone nuts, it's entirely possible he could have improved enough to win the Olympia after 1980. Samir would've smoked him in '83 and Haney would've eaten anyone but Arnold alive from '84 on (including Arnold after a time -- say, 1986 or so), but the '81 and '82 Olympias were wide open.
Oops! Except for, you know, Franco
for the fix winning in '81. Sorry