What if Mass Effect Andromeda is the greatest RPG of all time?
I am open to the possibility, but I consider it very unlikely by any well-defined standard you might apply to a video rpg. Even if it is very good as an rpg (and I find even that unlikely), "the greatest" is a hard nut to crack, given the great video rpgs that already exist.
it would have to be as varied in dialogue as the early Fallouts, FO:NV, Planescape: Torment and Arcanum. have a story as compelling and personal as that of the BG trilogy or again, Planescape: Torment, allow characters as varied in ability as your typical TES game, fully implement the three most prevalent gameplay styles (fighting, talking, sneaking) in ways that actually affect the plot and others' perception of your character rather than being cosmetic, and avoid gameplay/story segregation at all times.
How likely do you think is that?