There's a moment in Parasite Eve when, once you've upgraded a weapon into a cock-death dealing monstrosity that even makes Ray Charles flinch, that killing everything that was annoying you before becomes quite fun. And then you beat the game, and they stick you in a tower that has basically everything you killed and pissed off, deciding that your ass was quite delicious and they would like to have another.
Progression of character, via skills or weapons, is always a fun thing, but sometimes it just takes away from the purest element that you started playing and loving the game for. Case in point is Silent Hill, where finding a tuning fork and bubblegum might count as your upgrade for the location. And the bubblegum has one use, at which point you try to say the Duke Nukem line and then scream like a little girl as some random bloke with heads for feet eats you.
Oblivion suffered heavily from the "Final Fantasy 8" complex, where unless you found some way to cheat the system and rob a church or two, your weaponry was the only thing between you and an early visit between you and a skull polisher in the local Assassin's guild. In both games, you move forward, and all senses of accomplishment are thrown out the window the moment you are put outside the storyline and told to waddle from A to B.
If NEXON wasn't such bastards, then I'd recommend DFO as a source of "I spent HOW many hours playing this? Screw the hard guys, I'm going poke the level 13 monsters since I'm level 30." revenge.