About Mass Effect...
Like said, it's not a s much of a good and evil bar as a good cop or a bad cop bar. Plus it should be noted that it's two bars in there; Making hard decisions doesn't take away from your Paragon bar, and avoiding needless fights doesn't take away from you're Renegade bar.
So when you decide you'll help those brainwashed Salarians out of their misery even if it means shooting them in the face doesn't make you less of a Paragon, it makes you also a Renegade. I.e. if you have somewhat near same amount of Paragon and Renegade points at the end, it probably means your Shepard was a good guy who on the other hand could make tough or coldly calculated decisions when needed.
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Anyway, what bugs me most about most moral choice games is there hardly ever is a backslash for being good. That one last enemy soldier that begs for his life never comes back with reinfocements if you decide to let him go instead of killing him seeing his life is not worth the risk of you getting more trouble later on.
I find it annoyingly unnrealistic that cold, calculated and even cruel decisions would never turn out to be the better ones in the end, even if just out of dumb luck.
As these games are now you can be laughably trusting with your kind decisions and it never backslashes.
You could ask if it's really the evil decision anymore if it's in fact the correct one, but that's exactly where moral choice systems go wrong. No one thinks of themselves as purely evil, for christ sake even most psychopaths have excuses for their behaviour. There's more to being "evil" than the kind where you slice up townfolks for the kicks of it. It doesn't work too well for role playing.
The problem is that just that kind of evil is lumbed together with being ruthless, greedy, indifferent or egosentric.
Maybe these games should rather focus on different philosophies and attidutes rather than such broad and hard to define terms as good and evil.
And maybe sometimes letting that enemey live, no matter how he begs, when you're extremely vulnerable to an ambush the next thirty minutes should backslash.
So what if you get "bad karma" for your ruthlessness despite it being the right call? That's the grey area these games desperately need.