Type 1 RPG game:
Officially the role-playing genre of games is based on a few criteria such as can your character level up? (get stronger, more health) - Is it stat/skill based? - is it story driven, is there a lot of npc interaction within the game? (not cut scenes)
Type 2 RPG game:
For me an rpg can be all those, but an rpg game for me can also be one where I can get involved with my main characters personality, or use my own personality to make choices in the game that create consequences that effect the outcome of the story. So not every answer to the type 1 questions has to be yes for it to be an rpg.
Is 'stealth games' a new genre? It's easier to label things than have them floating around as miscellaneous. So I'd label Thief : DS as an rpg type 2
Very few fps even have a main character - just a shell with no personality and no ingame character interaction.