For me it’s Diablo II. Granted I’ve played my fair share of D2 since launch, and also recently on a private server with a comrade from hexbear, but I still feel like years later the game didn’t grab me as much as D1 did.
Granted I don’t hate D2, but for a game that I keep coming back to, D1 takes the prize.
I like TotK but the engineering mechanic is pretty laborious. You have a lot of freedom but only a small percentage of what you try works, and because of the clunky interface it takes a LONG time to make multiple attempts.