I'm most comfortable playing Neutral Good characters because it fits my nature in Real Life. I can't play Evil characters, and I can't play Neutral characters if being Neutral means "maintaining the balance between good and evil" or "being crazy". I can't play a Chaotic Good character because I don't believe that the end justifies the means and I believe that some law and order is good for people; but I can't play a Lawful Good character, either, because I would never put laws ahead of people's interests.
The D&D alignment system isn't perfect, of course, and it tends to be a bit misleading. For example, I don't believe that every Evil character is a monster who attacks everyone else on sight; it's much more subtle than that. Essentially, I believe that an Evil person is willing to do
anything to get what he or she wants, and he or she feels justified on the basis of his or her belief system. "Might makes right" is a good example an Evil philosophy. It doesn't necessarily make someone a monster, but it is definitely evil by all that Good people hold dear.
I don't think that a Good person should kill every Evil person he or she meets on sight. For example, even though my old boss is evil incarnate, I don't think that gives me the right to murder her.
When I play a Neutral Good character, I do fight against Evil, but I tolerate the existence of Evil creatures if they're not doing any harm and haven't done anything to deserve to death. On the other hand, I won't tolerate them rising to power, and if they already have power, I do my best to strip them of it (if I don't have to kill them).
Of course, in a hack-and-slash game like BG2, killing your opponents is usually the only option.
In some of my games, I experimented with a Chaotic Neutral character to see how well I could develop a Neutral philosophy. Whereas a Good character puts people's rights above all else, I think a Neutral character puts a "cause" above all else, even at the expense of other people's rights. My Neutral characters did not hesitate to kill anyone if they thought it served a noble purpose.
The leader of one of my Chaotic Neutral parties believed that too much power in the hands of one individual or one group of people is an evil thing, because power always corrupts. To her, there was no organization, group, regime, or institution whose very existence would not lead to exploitation and suffering. Her goal was to kill creatures who craved power for the sake of power, to destroy organizations who trampled the "little people", and to disarm the entire Sword Coast so that no group could dominate all other groups by force of arms. By her own definition, she was opposed to Evil, but I wouldn't call her a Good character at all.
