I always thought the classic DnD alignments system was incredibly simple. (Hey, two questions for ya friend. 1. Are you more Lawful, Chaotic, or in between. 2. Are you more good, evil, or in between? Done) And since the classifications are a little vague, it allows for great flexibility within each alignment (not all chaotic good people act exactly the same) but provide guidelines for how the character would act and how to roleplay them. The system also allows for tie-ins with rules systems (even more so in 3rd ed.). for example; spells that work differently on people/monsters depending on their alignment, DR and magic that are aligned with Good, Evil, Law, or Chaos, etc. Which makes it more than just an ethical/moral rp guideline, but gives it substance within a rules-based system.

I did like the Palladium alignment system, but found it slightly more restrictive than DnD alignment, and I felt they could use one or two more alignments to round out their system. I do think it works well for a super-hero rpg.

I wiki'd the 4th ed. alignment system. I will agree it is simpler, but at the cost of diversity and realism. It's the same as the previous system, they just axed Chaotic Good, Lawful Evil, and changed True Neutral to be called unaligned. I don't see the point of this, furthermore it seems by taking a more basic stance, they are insulting our ability to comprehend the old system.