A lot of responses here are way off.
It was Chuck and Wand as #1 back n forth depending on the day for years.
Then Rampage beat him the 2nd time. His chin 1st cracked in That fight. 1st time I think we went out. His style was very dependent on his chin (eat one to give a harder one)
After that it was more or less clear that Shogun was the true #1 since he absolutely destroyed Rampage and pretty much every LHW in Pride which had most of the top 10.
Him, Tito, Randy all declined at the same time as the best of Pride LHW. Chucks end of career run was sad as it is for many greats in boxing and mma who stay too long. All the lhw from the golden era are pretty much forgotten now.
At his peak which last for a few year I'd say given his reach, chin, power, tdd, he'd be a top 5 throughout the JBJ, DC LHW era.
I could see him dropping DC or Jon. He pretty much had death touch, maybe not quite as vicious as Rumble but maybe #2.
His grappling/wrestling defense was better than any LHW since aside from DC, JBJ, Glover.
Peak Chuck v Machida, Shogun, JBJ, DC, Rumble would be absolutely sick.
He may lose to most of those but wouldn't be surprised if he actually TKOs many of them