Once again it all comes down to perception. The Middle ages vary depending on where you look. It is compleatly different from Britain to Italy to Germany to Greece to the Middle East to China to Japan to South America to well you get the picture. It is also different in Fantasy Land, from Middle Earth to Wheel of Time to Song of Ice and Fire to whatever you can think of. Modern, well it's different from place to place too. Much of Fantasy is derived from Medieval times though.
I agree that Neutral and selfish are different. I would add to Lawful Good a tendancy to be Chivalrous (sp?) and good hearted. Lawful good would care about issues but would try to keep it in the realm of the Law. A Lawful good character would care if the peasants were starving and would try to give, he would try to hold to a more noble standard, but it would be the standard of the Kings Law. He would not speak out because the taxes were to high for instance (even though he might think it). They would make a show of how good and Noble they were but would not likely act on true right/wrong issues under the law.
Lawful Neutral would be the same as Lawful Good but without all the trying to be Noble crap. The Law is the Law, if the peasants are starving they should grow more food.
I got no Neutral but I don't thing self centered is it either. Maybe they are open to every possibility and not go to any extremes, The Lawful Good Lord is a Showoff, and Pompus, and the Lawful Evil Lord is a Heavy handed and overly cruel. They are both self absorbed goofs.
I guess it comes down to your definitions (quelle surprise).
