A buddy of mine said something about only certain types of creatures/characters (such as outsiders, alignment subtypes, and divine/profane classes) generate an "aura" for the purpose of Detect [Alignment] spells, thus, most normal characters wouldn't show up on Detect [Alignment] at all. Is this true? There is an aura gauge for "creatures", and by definition "creature" should include every type of character.
PHB pg306 creature: A living or otherwise active being, not an object. The terms "creature" and "character" are sometimes used interchangeably.
So, in the end, Detect [Alignment] spells should reveal a matching alignment aura on even a standard Human Fighter if their alignment matches the spell correct?
Edit: After reading and discussing these answers and after discussing the definition of a "creature" with my friend he is now under the impression that he was confusing it with 2e rulings.