Probably new vegas. I got caught in the hype of fallout 4, and it's not till you are done and sit and think about to realize how much petty time was wasted. Maybe it's the idea of getting somewhere exciting or the story getting somewhere that keeps you playing, or the the cheap habib of looting and collecting all these items, which don't lead anywhere significant, and the similarity of the side missions. The game is a great time waster/filler, but i can't think of moments of greatness, besides that terminator enemy. And the hours spent on building almost every camp, and defending.... The dlc's werent that good either. Fallout 5 better be a great evolution, in terms of story,  graphics, AI, physics, enemy types and the way they attack and respond/behave. But i doubt it. It will be a reskin on top of the old formula and same gameplay.