Amrûnril
Hero
Using a morality line, like in 4e, works well for those kind of things:
+50 +25 0 -25 -50
Lawful Good
<-Good
<-Unaligned->
Evil->
Chaotic Evil
I think that despite what we see on forums, most people understand the general difference between evil and good. So the DM just have to track the points (karma, fate, whatever) and choose the appropriate unlockable bonus with each category.
People will agree more often than not on whether an action is good or evil (though perhaps not in the cases where that question is more interesting). Trying to reach a consensus about how many points each act of evil or good is worth, though, is another matter entirely.
And I definitely prefer the framework of viewing Good/Evil and Lawful/Chaotic as orthogonal axes of variation. A character can be strongly commited to good while being firmly skeptical of authority (James Kirk, Harry Potter), or can be profoundly evil while idealizing order and tradition (Tywin Lannister, Grand Moff Tarkin), or can be strongly alligned towards law or chaos while remaining closer to neutral with regard to good/evil (Inspector Javert, Captain Jack Sparrow).