What makes a game replayable?

It’s fair to say I have played the various games of the Mass Effect series multiple times. I’ve even played Mass Effect Andromeda like four times. And it’s far from the only game I’ve replayed a lot — I’ve played through Assassin’s Creed Odyssey almost as much, I’ve got like six Kingdoms of Amalur plays under my belt, and don’t get me started on last year’s obsession Cyberpunk 2077, which I played an ungodly amount of and did all three life paths on. So what makes these games replayable? For that matter, I’ve been playing WoW for years, and that’s a game where each alt basically replays it, so the same questions apply there as well.

Honestly, I don’t have a real answer, because what makes a game replayable for me is of course not going to be universally applicable. But that’s part of the reason to ask the question, right? To find out why other players come back to a game over and over again. For me, it’s either because the gameplay loop is exceedingly fun for me or because there’s story nuance to be teased out on repeat play. For example, Mass Effect Legendary Edition doesn’t add any new content, but the content that’s there is extremely diverse and there’s a lot you can find on a repeat playthrough, and also, you can make different choices for a different outcome. And I love the combat in ME2 and ME3. The same is true to one degree or another for every game I mentioned above — Odyssey is just a ton of fun to play for me, the huge open world allows for a ton of exploration and side quests galore, and Kassandra is just so much fun to inhabit.

So then, what about you? Do you replay games? If so, why? What makes a game fun to play again?