Something about my personality has always demanded that I do two things when playing an RPG: play on the hardest difficulty available, and (with rare exceptions) only play through once, completing everything. I don't play on the most challenging level for bragging rights or to show off that I'm awesome – I do it because the most integral part of an RPG is the struggle. Be it good versus evil, man versus the world, man versus man, or whatever permutation of conflict the game can cook up, I have to feel like I'm fighting for a goal – and I have to feel like I’m fighting tooth and nail for every inch of ground gained. I've quit games that felt too easy or didn't challenge me enough because the whole time I sat there saying, "Who cares? Anyone could be winning this fight."
"Call it a hero complex, if you will – I want to save the day, and I want to overcome huge odds to do so."
I relish challenge, and even in the most infuriating moments of a game, the promise of overcoming that seemingly insurmountable challenge is enough to help me stay cool. In fact, it's a catharsis – becoming invested in the characters; in the adventure; in the grand struggle between forces is what drives me, but without the challenge, I just can't do it. Call it a hero complex, if you will – I want to save the day, and I want to overcome huge odds to do so. I want to be Ramza, Fei, the Bhaalspawn, the human Spectre, the Embryon, and the Harmonixer who's lost the one he loves, so that I can enjoy that delicious moment of victory when I at last turn things around.
This complex of mine ties in with a game's story, which is why I normally don't replay games. When the challenge of the gameplay and the climax of the narrative come together, that grand catharsis is the greatest moment of "this is why I play these games" I can have. When Taelus Shepard landed on the Collector ship and started charging all over the battlefield, one-two-shotting the Harbinger in seconds with the krogan shotgun, I felt a sense of satisfaction and justice. My power didn't come easily, and it only did so after a lengthy journey, but avenging my fallen comrades and stomping all over the self-satisfied fiends responsible made it worth every second. Those moments of story-fueled justice could never be recaptured in a subsequent playthrough – exactly why I don't replay games.