I like them to look unique and eye catching. I'm not asking for them to be models, but I am most drawn to unique features that only the MC has such as their hairstyle, the shape of their face, special features or their clothes. Things like that.
I guess that is why I was drawn to Sailor Moon, Goku from Dragonball, Magic Knights Rayearth, Batman, Superman and more. No one else in their series looks like them. You can recognize them right away.