It depends on when you look at them -- power levels go up and down all the time.
The Thing started at Class 5 strength, meaning he could lift 5 tons. His powers grew over time with repeated exposure to cosmic rays and other stimuli, making him classically a Class 85. In the 80's, he briefly evolved further into a larger, Class 100 strength level, but eventually reverted back to normal.
Thor and Hercules (at least, when they're gods) maintain a Class 100 strength level. (Class 100 really means lifting above and beyond 100 tons, the highest measurement point before they just stopped counting how strong a character was).
Colossus was Class 70 when he debuted, but received a permanent power boost in the 80's around the Fall of the Mutants, pushing him to Class 90-95 levels.
John Proudstar started at Class 5, as did his brother Jimmy. Through his time with X-Force, Warpath eventually grew into around a Class 90 strength level. A power boost he received during his secondary mutation increased him to Class 100 levels, but he has been significantly depowered in recent years, back down to around Class 10-15. Theoretically, the Decimation affected the additional strength he received from his secondary mutation just as it reverted Iceman back to human instead of permanent organic ice.
Juggernaut, of course, is typically a Class 100. Whenever he rebels against Cyttorak's path for him, however, his power levels weaken accordingly, putting down at around Class 50 or lower during his hero days with the X-Men and Excalibur.
Captain Britain originally was a Class 1 when he first got his powers. By the time of Excalibur, numerous revisions to his powers and abilities made him Class 85. Currently, his power levels vary depending on his faith and convictions.
Hulk is a baseline Class 70 as Gray Hulk, Class 85 as Green Hulk, and Class 100 as the Merged Hulk, with his strength level usually increasing at a variable rate with his rage.