The Pimp outplayed the Imp. Littlefinger brokered the military and marriage alliance between the Lannisters and the Tyrells, earning the gratitude of Westeros' two richest families and getting rewarded with the high-profile lordship of Harrenhal in the process. His intelligence network rivals Varys's, backed up with both a savagery and access to the royal coffers that the eunuch can't match. He's even made an overture to Sansa Stark; sincere or not, it opens up the North to his tentacles as well. It's only Varys's recruitment of Ros the red-headed whore to be a mole against her master that keeps Littlefinger from ranking even higher.