Tough one.
I think Super Mario Bros 1+3 or Super Mario World.
Those are not my favorite games I ever played. Zelda LttP and OoT, Fire Emblem, a few FF's, ToS are more immersive games, that dragged me into the game.
However once finished 1 or 2 times I don't have the need to replay them. I can always replay SMB1/3 and SMW, even after all these years, that's an amazing thing. So therefore I think they're my favorite games.