Let's ignore his 2 goals. The 2nd was a total keeper error.
Other than that, Messi had a hand in the other 2 goals Barca scored. Neither were assists, so neither will be counted in the stats. Both were penultimate passes - to Suarex for the own goal (so Suarez gets the assist) and to Alba for Coutinho (Alba's assist).
The fact is he played a major role in both goals, and no statistician will be able to see that. Again today, he had a wonderful run from the halfway line, destroying Jones, destabilising the whole defence, and then slipping in Alba whose cross just missed Suarez. Even if that went in, he would again get no statistical credit for it. And for good reason. "Penultimate passes" isn't a great metric - you could literally have a 5-yard pass from defender to midfielder, midfielder then finds a brilliant through ball. In statistical terms, both that hypothetical defender and Messi in the Coutinho goal did the same thing.
It's thus very hard to quantify creativity - find the "key" pass (or passes - Busquets had a massive role in the away goal) in a move. And I think Messi generates a lot more creative passing than Ronaldo, even in some bad games, which will go uncounted. Given their very similar goalscoring numbers, for me this is one of the differentiating criteria. The counter will be Ronaldo's movement creating space for others - it does - but this is even more subjective, and genrally in a GOAT debate you'd value on-the-ball creativity over off-the-ball runs, for the same reason that Gerd Muller never gets into the GOAT debate.
And without that quantification of creativity, we have 2 quarterfinals:
winning team 4-0, goals scored 2, assists 0.
losing team 2-3, goals scored 2, assists 0.
