This is a really hard question, but I’m going to go with Mass Effect 3.
The gameplay is easily the best out of any of the three games. I know that 2 and 3 get a lot of flack for being more shooter-y than 1, but combat in the first game always felt kind of awkward and clunky.
Three just has so many amazing scenes and mini-climaxes. I mean, remember Queen Thresher Maw vs. Reaper? Or Mordin in the dispersal tower? Or Legion asking Tali and Shepard whether he has a soul? Or the combined fleets coming through the relay to retake earth?
The whole game was one big farewell to the characters and setting and plot that I’d grown so attatched to, and I loved it
Plus it’s literally the only video game that has ever made me cry.
and I cried
three or four times even