George forman’s power compare to today’s super heavy’s

This. Foreman's skillset is extremely underrated. Only Ali and Young, who both have impeccable footwork, handspeed, and timing were able to completely neutralize big George. Holyfied, Morrison, and Briggs were able to get decision wins over Foreman in his comeback, but nobody came close to neutralizing Foreman's power like Ali and Young did.

Foreman vs. Ali

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Foreman was able to use his short hooks to the body to get Ali to the ropes, but underestimated Ali's timing and handspeed. At 39:20 Ali hit Foreman with a quick 1-2 and then a right hand to back Foreman up. However, Ali realizes he isn't getting enough power in his right hand, so Ali at 39:40 pushes Foreman back to get space and takes a step back and loads up his right hand on Foreman with his feet in better position. The right hand slowed Foreman down for the rest of the fight. Ali was also managing to get Foreman to walk into a lot of his straight right hands and check hooks.

Foreman vs. Jimmy Young

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At 7:11 Young constantly varies up his footwork and manages to stay a step ahead of Foreman and before Foreman can get his feet in position Young beats Foreman to the punch and connects on Foreman with a right hand. Also, in all the clinches Young would constantly throw a short uppercut to Foreman's body, which explained why Foreman was sucking wind in the later rounds. An example is at 18:11 where Young tags Foreman with a well timed uppercut to the body while in a clinch. Ward used this same tactic against Kovalev in their first fight after the knockdown, which resulted in Kovalev having nothing left in the tank in the later rounds. Young was also landing a lot of straight right hands on Foreman, by beating Foreman to the punch before Foreman could get his own punches off.

Young did make a serious mistake at 19:32 by getting sloppy with his footwork, which allowed Foreman to get in range and land a short left hook to the body, which put Young in position for Foreman to land his powershots. However, Foreman feet were in poor position, which resulted in Young taking the punch and going back to work to outpoint Foreman.

 

The speed bag and jump rope are great for maintaining good balance and also building strong shoulders, forearms, and triceps. The heavybag is also great for building up strength, since training several rounds a day on the heavy bag will make keep back, chest, arms strong. The medicine ball is also good for gradually building up more functional strength, which can help generate more punching power.

Shane doing 1 round on the heavybag and some light shadow boxing.

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Using proper technique on the heavybag while also hitting the bag with power for 3 straight minutes builds up strong arms. After Mosley finishes on the heavy bag he moves on to shadow boxing. To make it more challenging and to build more strength you can include 2lb dumbbells, but never heavier.

GGG doing 3 rounds of shadow boxing with 2lb dumbbells.

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Golvkin keeps his shoulders parallel with the ground and turns his shoulder just right while also maintaining excellent balance, which results in GGG not wasting energy. Some of the other guys aren't turning their shoulders enough and aren't keeping their shoulders parallel. The result is them being arm weary quicker and having no snap on their punches. GGG on the other hand is still full of energy die to his efficiency. GGG's foot work in the video is always excellent, since he never throws a power shot unless his feet are in the right position.

Excellent fighters from the past effectively using the speed bag.

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At 3:30-5:50 all of the fighters are hitting the speed back with proper punching mechanics that can effectively transfer their power while also keeping their upper body in excellent condition. Sugar Ray Leonard was very efficient on the speed bag as was Marciano, Holmes, and Ali.

Too many fighters get sloppy on the speed bag and develop bad habits. But, when the speed bag is used effectively it can help a lot with punch accuracy and transferring power efficiently.

Joe Louis using the medicine ball

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At 25 seconds Louis is letting the medicine ball connect and then quickly returns it. This builds sharp reflexes and with arm fatigue. I see even experienced fighters catch the ball with letting it connect and return the ball, which is a wasteful motion. By having his feet in the right position
Louis can let the ball connect and quickly return it all while using very little energy.

Max Baer on the speed bag

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At 35 seconds Baer uses the speed bag very efficiently and effectively shifts his body and turns his shoulders, which allows him to transfer power to the bag as well a time the bag.

 

noone today really applies it like foreman.

 

Power is not everything. In fact, my guess is that the hardest punching heavyweights aren't necessarily famous boxers e.g. Jimmy Thunder and Courage Tshabala.

But back to the original topic, I think Big George would be comparable to today's heavyweights but I can see Big George tripping all over himself trying to hit Chris Byrd.

One thing that's been pointed out in this thread, sort of, is that smaller heavyweights like Haye, Breidis, Tyson etc. are effective punchers because they can be mobile and not lose their power and accuracy.