my favorite game in the series is 358/2 days. this game makes me SOOOOO bawling my eyes out rolling across the floor. I love axel, roxas, and xion's friendship and their story it's so tragic and twists my brain I love these characters and the everything. I own both the novel and the game!
my second favorite is either chain of memories or kingdom hearts III. kh3 introduced me to the franchise, and I like the worlds sora goes to and how everyone kind of joins together as a team finally (lol). but I loovve chain of memories's entire story and I'm just a big organization 13 enjoyer. they are silly and fun to me. in my head.