Im just going to give an opinion on how. You dont have to go my way, but im gonna lay down my suggestions.
RPG:
A good RPG mod/game needs to have plenty of depth. Not like 5 min's of talking then your shipped out on a hour long killing spree to advance (NWN main campaign). Im talking like Its mostly a vocal game, with battles and quests to go kill here and there. Im gonna need to come back to explain this one.
FPS:
Reality: Only one mod ive played so far has met my reality Grade of A. Project reality.
I love the feeling of not knowing whats around the corner, to have your weapon always in ironsights.
The Pleasnt rush of being air-dropped from a helicopter into an enemy hotzone
The tense feeling of knowing your getting supressed by the enemy
Wide-open Maps, 32-on-32 maps with key points needed to accack, so combat is semi-focused
The "oh god" feeling of knowing your death is near, and fast approaching.
The questionalbefeeling of a motor in the distance. Is it friend or foe?
Its something im looking for. I dont really mind if its Modern or WWII. I know it isnt the best explination, but ill try and edit it as much as i can.
Regular: Total Conversions are all im mostly looking for here. I know some dint really accept it like that (L4D) But people make the most of it by just adding loads of content that'll make the game all the worthwhile (Monster Factory L4D mod). Then theres totally moddable games (HL series, Crysis) Being taken to WHole entire new levels (Mortewood Plaza for HL2, Revolutionary Zombie Game for Crysis) And please for the LOVE of god make a commitment to release and dont just post it and knock it because it was too big (RZG is kinda leaning like that, and like 30-35% of HL2 Mods)
I agree with everything you are saying. Storyline is very important, and it's great to have huge story changers in the game. Like for example, maybe you are taking over a city or something, and one of the main characters who you had as a "Side Kick" in the previous levels dies, and if the story is good, you actually get a feeling of sadness. That would basically be like your "Not knowing whats going to happen around the corner" type of feeling.
Well, I'm not the only one who thinks that way about games... whew!