Why are Michelin's considered the best? I don't think they are "the best" any more. They are one of the best IMHO. 30 years ago Michelin tires were better because they had invented the radial ply tire in the late 1940's and the other makers like Firestone, Goodyear, and BF Goodrich were mostly selling bias ply tires. So in the 70's Michelin had been making radial ply tires for 20+ years and they knew how to do it right.
In 2013 there are many good tire makers. Quality of tires is very high. Same with cars. Cars from the 1970's had many many more defects than today's cars. Again quality is very high today.
I do like buying tires made in the USA as I think tires made here are made for USA conditions. There is no Yuma or Florida or Texas in Japan or Germany. No really hot places. USA tire makers take USA conditions into consideration when they make the tires. But that said I am sure tires made in industrial first World countries are all good. I would never buy a tire for my 40,000 pound RV from a non industrial or non-honest place. Like Mexico, India, or China. I don't care if they were free.