Geralt cannot be a Mary Sue by the fact that he is a pre-established character. Therefore players aren't placing themselves in the game rather than taking on the role of another character. Custom-made characters are closer to acting as Mary Sues but only if they are doing so in a narrative that's already been revealed to the public, and they make broad changes according to their desires. Unless the player installs mods that greatly change the effect of choices and endings, then they're only playing the game within its rules.
This Geralt not even close to Mary Sue. On the other hand Inqusitor is definition of Mary Sue.
Mary Sue stories—the adventures of the youngest and smartest ever person to graduate from the academy and ever get a commission at such a tender age. Usually characterized by unprecedented skill in everything from art to zoology, including karate and arm-wrestling. This character can also be found burrowing her way into the good graces/heart/mind of one of the Big Three [Kirk, Spock, and McCoy][Cass Cullen Leliana :lol: ], if not all three at once. She saves the day by her wit and ability, and, if we are lucky, has the good grace to die at the end, being grieved by the entire ship.
We not die yet. The you think Warden is Mary Sue too.