Actually FFX was predictable. I knew Seymore was evil, I knew that Yevon wasn't "good" and knew that the Summoners had to sacrafice their lives and the lives of their friends to start the cycle over. The game was highly predictable in events and who is bad or not. It was a major let down.
As for Video game rules...saddly this applies to RL instances and Movies XP. Usually those with power will see themselves as "Good" unless they actually state otherwise.
I'm happy that I don't believe in the concept of good or evil, only Intent and consequence.