JLXC, I think you have an interesting viewpoint; however, I think you're confusing "good" with "heroic." And I also think that there are plenty of really fun ways to play RPGs without being a saintly potential martyr.
Personally, my favorite characters are NOT heroic by nature. I like playing characters who believe in doing good works, but who struggle with issues like fear, selfishness, laziness, and the like. If they eventually perform a heroic task, kudos; but if they don't, well, I'll have fun getting inside their heads.
Paladins, however, are different. They don't just have to be good: they have to be heroic, IMC. Since there's no "ends justifies the means" for a paladin, they don't get to be sneaky or dishonest.
Daniel