Yeah, the Dementors' habit of soul-eating makes them a tough call. If they're not truly sentient beings, calling their survival instinct "inherently evil" would be like doing the same for ravenous wolves, with the main difference being that the latter would rip out your throat rather than your soul.
Anyway, I'm trying to envision how a Nintendo-themed one would look:
LAWFUL GOOD: Mario, due to his self-imposed obligation to rescue princesses
NEUTRAL GOOD: Link, as he has a tendency of unwittingly becoming a mythical hero destined to save Hyrule
CHAOTIC GOOD:
LAWFUL NEUTRAL: Yoshi, I suppose...
TRUE NEUTRAL: Pokemon, whose will is that of their trainers'
CHAOTIC NEUTRAL: Wario, whose only motivation is greed and personal gain
LAWFUL EVIL: Ganondorf, whose character is strikingly similar to Voldemort's
NEUTRAL EVIL: Bowser, who's just into the whole "evil" business for the chicks and power
CHAOTIC EVIL:
It's still a work in progress. I'm open to suggestions, of course.