Ah, semantics... Ok, you said
"I don't often class Dungeon Crawlers as RPGs. They have characters of course, but those tend not to be unique personalities that interact with the game and NPCs of the game ~not in any way deeper than buying and selling, or asking for rumors in the best of the best examples."
So, my response was directecly to that - that I would not exclude, universally, dungeon crawlers as RPGs; and proceeded to give examples wherein a game that some
might consider a dungeon crawler I wouldn't, even though others I would.
So, that wasn't a universal statement that if a game
did contain those mechanics that I would consider it an RPG. There are other factors, as I implied.
So, in regards to "No One Lives Forever", shoot me, but I haven't played it. However I may consider it technically an RPG if the mechanics were exactly the same just in a different genre than high fantasy; though I'd more likely consider RPGs within the fantasy genre. If I played it, I wouldn't be thinking "wow what a great RPG", I'd be thinking "what a great FPS!" (ymmv) - even if it did incorporate some RPG mechanics in the player/character development.
As I mentioned above, a dungeon crawler that's on rails I wouldn't consider an RPG.
An FPS with RPG mechanics I'd hesitate to call an RPG overall.
I think I'm sensing two aspects to an 'RPG' in my preferences. One is genre, of the environment, story, etc; and one is the character building mechanic. Having the latter with a high fantasy setting for the former, yeah, I'd instinctively call it an RPG. Having the latter in a non-fantasy setting (like a distinct sci-fi for example), and I may consider it an RPG style game but I'd have to get over the fact that it's not fantasy

. You could have the game an RPG in a fantasy setting but a different style of game - overhead crawler (Diablo), first person crawler (BT), first person 3d (Elderscrolls), etc. By my argument, I'd say you could have the exact same game styles in a sci-fi context and still have an RPG (Kotor comes to mind, or System Shock); but I haven't played enough of'em to name some off the top of my head
I'm not sure I best expressed what I was thinking, so hopefully you get the gist

Keep in mine this is what
I think of when defining RPG; others may not think the same. =P