A: Actions that everyone at the table enjoys.What is good Role-Play?
It's that simple, and that hard. What any given individual enjoys doing with his/her character is going to differ for each given individual. What the other individuals in any given game group enjoy watching and interacting with is going to differ for any given game group.
Some players are there to escape the daily grind by hacking some orkz.
Some players are there to plumb the depths of a fiction characters psyche
Some players are there to make their friends laugh with puns and in-jokes.
Some players are there to try to solve the sorts of problems they couldn't in real life.
Some players are there to show off their mastery of an abstract rules system.
Some players are there merely to hang out with their friends.
Some groups are going to enjoy deep immersion
Some groups are going to enjoy being able to solve problems by killing the causes of such problems.
Some groups are going to enjoy high intrigue and keeping secrets in charcter
Some groups are going to enjoy playing a tactical minis game some one-liners and funny voices tacked on for humor
Some groups just use the game as an excuse for beer.
Yet,
So long as the interests of each player and the interests of the rest of the group are aligned well enough that nobody's enjoyment comes at the cost of someone else's misery, that's good roleplaying