I don't always care about the morality of my decisions but it is nice to see them reflected in certain games.
Take New Vegas, for example. I didn't find myself helping the NCR promote democracy because it was "the right thing to do". I did it because I liked democracy just as much as they did. Helping an alpha male warlord like Caesar take over didn't line up with my preferences. Plus Howard Hughes (or whatever his name was, I forget) had all those cool robots. Of course they wound up under the control of Yes Man soon thereafter but...anyway.
I think you see my point. Morality doesn't necessarily have to be a factor in the decision making process. As a matter of fact, it would be completely fair to say that some of us do shit almost purely for the lulz.
To be completely honest, I have to admit that my way of thinking isn't necessarily dependent on traditional concepts of good and/or evil. Sometimes I like to maim bad guys simply because fuck bad guys, that's why. On the other hand, becoming the bad guy is...well, it's just kind of boring, really. Why go after civilians, for example? There's no sport in it. They can't fight back and it's not like you get points for them. Taking over the world? Ha! Why would any sane man want to be cursed with such a responsibility? The surest way to make yourself a slave to everyone, is to let them think of you as their master. After that they'll blame you for every shortcoming their lives may have, be they real or imagined.
I guess what I'm trying to say is, the more I think about it, the more I realize that I simply enjoy playing the good guy. Not out of a sense of responsiblity or honor, but because it's more fun that way. Plus I'm less than forty-eight hours away from opening up Arkham City and I'm thinking, would it really add anything to the experience to be able to play Batman as "evil"? What would he do then, carjack people? HA! He can basically fly already. So why bother? And who's to say that he's not evil already? Doesn't he operate from mostly selfish motivations to begin with?
Think about it. Let's say you're Tommy Vercetti, and you've already won what you wanted from Vice City. The nicest cars, the biggest mansion, any woman you meet. What then? Would you just sit back and wallow in the decadence of it all? You'd eventually get bored, you know...then one night, you might find yourself thinking.
About how you miss the challenge of the good old days, when you had to fight to survive on the street. Next thing you know, you're out there in highly modified body armor beating the raw shit out of dangerous criminals simply because you can. Just for the thrill of it all, the "lulz" as they say.
And really...that's not such a bad thing, now is it.