There are two important protein criteria to consider: Bioavailability and protein "completeness". 

Bioavailability concerns the absorption and protein efficiency ratios of the protein - the more bioavailable the more is absorbed and used by the body. 

The "completeness" aspect has to do with how much of the 9 essential amino acids and how many of the 21 total amino acids does it have.  More amino acids means a more complete protein.

Typically, this is the best order of protein sources: Eggs, Milk, Meat and Fish, Soy, Hemp, Nuts, Wheat.