Sometimes, I just want to play bad just to be bad.
Like playing the Joker in any Batman game that lets you.
If the character is psychotic, then destroying the world (and yourself in the process) isn't unrealistic.
The psychology of it is that even though the world is gone, YOU did it, proving that YOU are the most relevant / powerful person ever.
Of course, I'd make the game have multiple endings based on events.
Really, it could just even be a scaled-up version of Counter-Strike.
in general, being the good guy sells better, but, as there are plenty of games like that, games like GTA and others usually sell very well.
The popularity of Saving the World suggests it will have more Players. People are generally Good in the real world, and reflect this in their Virtual Avatars. Good and Evil are Factions. Factions inevitably form in a Online Game due to beliefs. Both Factions believe they are Right in their beliefs, while the opposite side is Wrong in theirs. Thus destroying the world can be equally satisfying, depending on your beliefs. In my opinion, the goal shouldn't be to explicitly define Good and Evil, but fuel both points-of-view with enough information for players to choose one of the beliefs and defend it. The success of the game depends on how well you can keep Players engaged, defending their beliefs. A good fire needs fuel, fuel the Conflict my friend.
