I mean, is there any argument against it? Yeah, the title is a bit hyperbolic but i really believe it is the GOAT, here are some of the reasons:
- Best protagonist
- Epic storyline
- Most realistic open world
- Great writing, dialogue and characters overall
- Beautiful graphics (on 360 at least)
- Wonderful shooting and horse mechanics, what else do you need in a western?
- One of the best, if not the best ending of a video game
In resume, it's a masterpiece.