UTQG stands for Uniform Tire Quality Grading and every tire on the market (aside from snow tires) has a rating. The rating comes in three parts consisting of the treadwear, traction, and temperature grades. Just like in school, a high number is better for treadwear, and higher letter grades are better for traction and temperature. I suggest some light Wikipedia reading if you have the inclination and time to spare.
I am working on creating a master list of tires arranged by their UTQG ratings for easy comparing. Some tires have multiple ratings depending on size and for the purpose of this list, I will take the best rating any tire has. This is still a work in progress, but this will be updated frequently.