Omega Vision
Face Flowed Into Her Eyes
If you asked Stan Lee, I'm sure he'd tell you that Thing was supposed to be stronger than Iron Man in the beginning. Unless I'm mistaken, there was a handbook from the 60s (and yes, I know handbooks are secondary evidence) suggesting that Thing and Namor were the strongest beings after Thor and Hulk, with no mention of Iron Man (of course I also remember Spider-Man being considered in the top 10, so...).
I'd be willing to say that current Thing and current Iron Man are physical peers, but as a few people have pointed out, strength and durability aren't everything.
Hell, if you limited Iron Man to just using his strength, durability, and flight he'd take a majority based on that alone. Add all his other powers and Ben doesn't stand a realistic chance of taking 1/10, but if you expanded it to /100, he might take 4 or 5/100 based on tenacity and luck.