Heres how Strength level goes in the Marvel Universe as far as i can tell from the web and previous comic encounters. Note that a writter can do pretty much what he wants once he has undertaken a project, strength levels are only used as refferences.
Incalculable
Galactus
The Watcher
Odin
Class 100 +
Hulk
Thor
Silver Surfer
(All 3 have no know limits to their strength, potentialy limitless in all 3 cases though Silver Surfer was once outmatched by Hulk, he resorted to throwing Hulk into deep space, where he just waited for some time)
Class 10 to 95
Venom 25
Namor 40 out of water
She Hulk 75
Thing 90 (Most likely higher du to cosmic raditon levels rising in his body,he may now be a 100 + class, though he does not have limitless strength as Hulk,SS or Thor.
Juggernaut 95 (Always had the uper hand on Colossus before, i have not yet seen him vs Colossus since his "upgrade"😉
Abobination 95 (Has some strength boost once enraged, nowhere near the Hulk.)
Colossus 100??? (Recently increased as an adult)
Bottom line, not taking under consideration that Marvel would never allow Colossus to defeat Thing, i believe that, considering numbers and real comic book history, Thing would win 8 out of 10 matches VS Colossus.
Thing Wins