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.
Honestly I fucked with DA2. I liked the idea of having the whole game center around a city, and playing through vignettes of a major person in that city's life. Where it fell short for me are the same places DA1 fell short - the writing was fine when it was building up a conflict, but fell to pieces when it came time to resolve that conflict. Oh I'm sorry did you think that this was all about how some institutions dehumanize their victims and cause the very problems they seek to resolve? Actually it's just a demon and every single bigoted person gets totally vindicated.
I didn't mind it being smaller in scope either. I liked that. The main issue I had was with the gameplay. It was action oriented and really removed the strategy from the game aside from a few minor things. Spawning enemies out of nowhere and constantly using the same map over and over and over again. It was a half-baked game unfortunately.
It was rushed af… it was completely developed in like 16-18 months. Given that, it’s pretty good.