Final answer:
Tom and Daisy found Gatsby's party loathsome due to its chaotic atmosphere and lack of refinement and sophistication. Gatsby, however, measured his party's success on Daisy's happiness, aiming to impress and win her affection.
Step-by-step explanation:
Tom and Daisy found Gatsby's party loathsome because it was chaotic and unrefined. The guests at Gatsby's parties were not from their upper-class society circles; they were new money and celebrities, which the old money, like Tom and Daisy, looked down upon. The parties lacked the exclusivity and sophistication that they were accustomed to. Gatsby measured the success of his party by Daisy's happiness. He threw these lavish parties with the hope that Daisy would attend and be impressed by the spectacle, rekindling their past romance. His measure of success was deeply personal and directly tied to his feelings for Daisy, rather than by any general social standards or expectations.