It really depends on who they're fighting. If you don't consider other champions or contenders, you could pose a strong debate for Foreman or Tyson because both have the power to end a fight with one punch. However, once you consider the other men who have held the title throughout history, you have to compare these three to all of them.
Given these comparisons, Muhammad ALI has a better chance of defeating --or not losing to-- the majority of the other champions. He has something that no other heavyweight boxer in history has. He has perfect symmetry and balance. When you consider this, there are other champions you must consider.
Larry Holmes is the best reason that ALI stands above both Foreman and Tyson. Lennox Lewis and Joe Louis are also good reasons. All three would beat both Foreman and Tyson because they have the tools to nullify the power of Foreman and Tyson. Both would be reduced to just power punching and ultimately defeated.
Holmes, Louis and Lewis would all have trouble with ALI's speed and balance where all would find ways to defeat Foreman or Tyson.
There's your answer. When you stand these three against other champions, Muhammad ALI stands firmly above both Foreman and Tyson.
Muhammad Ali despite his greatness had sloppy technique. He left his defense wide open at times and threw lazy punches when he felt like it. What made him great was his superb athleticism and reflexes. He got away with almost anything simply because he was that talented. But unless you have the same level of athleticism as Ali, you'd probably get creamed using his style.
George Foreman relied more on his physical strength and toughness. Pretty much a great slugger, but I still would advise against it unless you're gifted with natural physical strength.
Tyson of the last decade, well he had almost no style. Pretty much a one punch gambler. But prime Tyson on the other hand, that's a different story. Tyson in his prime used lightning fast combos, with any of his punches (even grazing hits) having knockout power. His defense was one of the best (if not the best) defenses ever in heavyweight boxing history (I mean, go show me another heavy weight with as good defense). He was also pretty darn fast, not just his hands but his foot and head movements as well. Plus Tyson's style was surprisingly very effective against bigger opponents. Tyson was a complete package during his prime and was pretty damn unstoppable. Shame he lost it. But what's a bigger shame is that most people only remember Tyson from his older years but have forgotten what he was like when he was champion. Because of the laughing stock that he now is, people don't give him the due respect of his greatness back in his prime.
But yeah, if we're talking styles, then Tyson by a pretty wide margin. If you dont' believe me just watch a few of his prime vids on youtube. You'll see what I mean.
Sometimes I think that people are trying their hardest to convince others that Mike Tyson was the best ever, but that is not true. The others that you have mentioned, they had longevity and did not end up a laughing stock like Mike. Ali and Foreman fought way better competition than Mike ever encountered. Iron Mike was a one hit wonder that disappeared into the air, a flash in the pan, never to be heard from again, except to share a laugh. George Foreman in his prime, like Tyson did not have a style, just a overwhelm your opponent and take him out mentality. That style will not work against a sheer boxer with fantastic foot work, blinding hand speed, and cat like reflexes. Remember this finesse style was the recipe for Iron Mike's demise against James Buster Douglas and Big George Foremans defeat by Jimmy Young on March 17 1977, in San Juan, Puerto Rico,that forced a prime Foreman to retire, after losing a unanimous 12 round decision, and being decked by Young in the last round.. In all a prime Muhammad Ali's style was the best, 1964-1967.
there is no such thing as a better style, each style works well in certain situations. George Foreman beats Mike Tyson style fighters( as shown in his destruction of Joe Frazier), Mike Tyson type fighters can beat movers, jabbers, and orthodox boxers like Ali( Joe Frazier beat Ali the first time, before he adjusted his style and learned from his mistakes, and Ali beat Frazier the next time), and movers like Ali can always beat sluggers/brawlers like George Foreman. It's not cut and dried, tons of fighters break the mold, and mix different styles.
No one had a better style t han the other. They were all differently physically so each style matched their physical attributes. But since most heaveweights wont have the style of ali or tyson then I would say forman style was more effe4ctive.
It's obvious that Ali had his own style that went against the grain of the natural boxing technical teachings. Slip straight punches rather than pull the head back, bob and weave,etc. But because of his speed he got away with it for awhile. Later, laying up against te ropes and taking endless blows, caused IMo a lot of hs troubles today. Foreman, as you say relied on his size and enormous power.Tyson was technically taught by the old master, Cus D'amato, but later relied on loading up for one big shot, which was his demise, IMO. Tyson had all the tools at one time, but blew it.
I would say, since Mike Tyson never lost a fight, his style was easily the best.
Muhammad Ali was fast ,moved quickly and punched with pace .Foreman had great punching power while Tyson was effective in close range fights ,so what you think which boxing style is more better ?
