Dude. Don't be thick.
No one disputes that Park didn't play the final, nor that Nani scored a penalty in the shoot-out. But look at the previous two months, as opposed to the final 19 minutes of the season, and you see an entirely different pattern. With the exception of those 19 minutes, Ferguson greatly preferred to use Park over Nani. This is a simple fact. It is not my opinion.
At the moment, Park is superior in the one most important aspect of any football player's game - helping the team to win.
Nani has more natural talent than Park, it is true. Obvious, in fact. But world football is littered with the wilting careers of men with more talent than our Park, but who became less effective football players. I truly do hope that Nani reaches his potential, which is vast. But until he does, it's just potential. He can fulfill it, but he might not. He would do well to cultivate the focus, drive, and discipline of a player like Park, and of course any young footballer would benefit from Park's experience, which is considerable. And it is in these attributes - not specifically part of a winger's game, but certainly part of a footballer's - that Park is simply better. And it is for this reason that he better helps the team to win at the present time, and it is for that reason that Ferguson keeps putting him in the team. That won't change at all until either Park gets injured, or Nani steps up his game - hopefully the latter. But do not underestimate how difficult it can be for young players to develop those attributes, and do not underestimate their value to a football club.