Ruiz went 5-5-1 (1) 1NC in WBA HW World title fights and he lost a WBA Title Eliminator to Chagaev. The NC was a decision loss to Toney but was later changed when Toney tested positive for a banned substance.
2-2-2 in HW World Title fights, 2 wins over Patterson, 2 stoppage losses to Ali. Liston is overrated around here. He was great, but doesn't deserve the high ranking that many give him... he's not top 10 in my opinion.
There was never a period of time where he was number 1 the same cannot be said for those I've listed. Bivins spent a longer time as the next best and he compiled a better record during his career but I would call him one of the best champions.