60% aesthetics, 40% gameplay, but I won't keep playing a game if I can't get both.
I like monsters, creatures, and demons. Firebrand, Dormammu, Shuma-Gorath, Blanka, Oni, Zato/Eddie, Dizzy, Bowser, etc. Preferably evil.
In terms of gameplay, I love space control,
especially characters that can hit you from anywhere at any moment. Zato can spring Eddie up from under puddles, and Dormammu has Purification. I would say Zato and Dormammu are my favorite FG characters ever right now. Street Fighter has nothing that satifies the gameplay desire. Smash doesn't have a character that has aesthetics and gameplay - I have to choose one or the other. I am hoping Mewtwo is good for both.
BlazBlue has Arakune, but his execution is leagues beyond my abilities the last time I played. I also think he is "gross" because he is a mindless wretch. I value intelligent characters a lot. Firebrand and Shuma-Gorath are "monsters", but still intelligent. Plus, Arakune being a puddle of goo because man "went too far" is a turn-off for me.
It's all rather complicated...I can explain more if you want me to, but I suppose this is more than you wanted.