The Ali that smacked Cleveland Williams from side to side beats Lennox, but it could be his toughest test. It's worth remembering that Ali danced around and through combos for 15 rounds in his prime, Lewis generallly moved much less and through mainly jabs and mightily loaded right hands. Ali has a big edge in stamina then, and is renowned for having the best movement and hand speed in heavyweight history. Ali was also freakishly tough with supreme recuperative skills. The same cannot be said Lennox. Although he didn't have a glass chin as some say, he wasn't solid either and Ali's KO of Folley and Williams show that he had some dig when he needed it. Ali moves in and out, trading punches with Lewis in a two sided display of masterful boxing, if not the most exciting. The first half of the fight is close, but as it wears on, Lewis slows whereas Ali grows in confidence. If it's 12 rounds, Ali by UD. If it's 15, and exhausted and bloodied Lewis is dropped in the 14th and cannot beat the count. Not a Thrilla in Manilla, but a flawless victory by "The Greatest."
A better way to look at this, is to ask which potential opponents would pose the most serious threat to him: Swarmers Joe Frazier would always have been a stylistic nightmare for him. I also think that Marciano might have beaten him for stylistic reasons. Other pressure fighters might also have posed a risk. Punchers who used pressure behind the jab Ken Norton employed this tactic to good effect, and it is possible to imagine somebody like Louis, Liston, Lewis or Wlad doing it, with a near perfect fight plan. Fighters who made him work on the front foot Ali was very effective against anybody who came after him, but when somebody ran from him he seemed a little lost. Maybe, just maybe, somebody like Gene Tunney, Tommy Loughran, Billy Conn, or Joe Walcott could have frustrated and outpointed him.
This is what I was thinking to, only better put! But Liston? The concensus here seems to be that Liston was passed his prime when they fought, I think that is unfair to Ali. Liston was the champion, he had destroyed Pattersson and was considered unbeatable. Anyway, I think footwork is one of the keys to beating Ali, you don't need to be as fast as him of course (who was?), but fast enough to keep up and good enough to cut the ring. Liston was lacking in that area.
I'm stooping to your level but as usual it's over your head. Try to keep up. It's par for the course with your inventive posts. Tyson was fed Ali clones since his inception. With all the clones following in Ali's footsteps, Cus saw this and knew which heavyweight style would flood the scene throughout the 80's. So Cus got lucky and was introduced to Big Head Mike at an early age, thus finding his answer to the fleet footed boxer. He knew a thing or two about Ali's style, I would think. If anyone would be considered the favorite over Ali in a prime battle head to head, it would by Tyson. Cus taught his boy well.
Langford, Johnson and Dempsey are terrible shouts. You haven't even seen a frame of Langford fighting and just about every second we have of Johnson footage suggests he'd have absolutely no defence against Ali's double, triple jab and combos. It would make the Williams fight seem competitive. Dempsey at least had head movement, but chasing Ali with hands at your waist isn't really ideal. Tyson would give Ali his hands full definitely, though, and Vitaly and Wlad I both favor against Ali.
Why Vitali? I can see the argument for Wlad boxing behind his jab and using his good footwork, but Vitali with his hands held low and his more agressive tough-guy style seems more suited to Ali, although the size would clearly be a problem.