While I think the 'star rankings' as issued and averaged, for example, by the several 'pros' in the college football recruiting realm are about as good a general way of comparing classes as any out there, I can find fault with them on several levels.
For example, rating players from 1 star (I assume they do assign one star to the lowest 'rated' players but I don't recall seeing one rated a 1 star) upto 5 stars is simply far too few strata or levels to be reasonably meaningful. I would suggest they should rate players on a 1 to 20 scale or something so that there is more indicated difference amongst players. I believe many also assign a numerical rating as for example, player x is the #21 rated DT. Perhaps the better way to grade an entire class would be to take the numerical rating of each player and add them up and divide by the number of recruits to yield an average player rating such as 21.5?
Even doubling the number of stars from 5 to 10 would help.