Kanto: Lorelei by far.
Johto: I like Morty, especially after his retooling in HGSS. I always liked Jasmine too. Recently, I've been feeling a soft spot for Pryce.
Hoenn: Winona is my favorite of the Gym Leaders. Steven is my favorite overall - I like how helpful he is to the player.
Sinnoh: I really like Aaron despite his type of choice not being my thing. I also love Cynthia. As for Gym Leaders, I like Roark, Fantina, and Byron. I'm probably the only one who likes Byron.
Unova: Probably Grimsley. I love Cress too. I also like Elesa, Lenora, and Caitlin. I also kinda like Marlon. And for the first time, I love the protagonist characters.