20XX is a meme in the Super Smash Bros. Melee community where it is said that in the year 20XX, everyone will play Fox (the best character in the game, albeit the hardest to play at his max potential), and they will have mastered the game so precisely that games will essentially be decided by the initial game of Rock-Paper-Scissors for Port Priority (which affects things like who gets grabbed if both players grab on the same frame).
Marth, meanwhile, is considered a good character in Melee, but hasn't won a National in many, many years.
Cue this year's Apex, which was the biggest Smash Bros. tournament of all time, where Melee Grand Finals is between a Marth player and a Fox player, and the Marth player won, despite that player having barely played the game since last year's Apex (which he also won, but not with Marth).
