The former Bristol City and Celtic midfielder enjoyed a dream debut, scoring a hat-trick of penalties at Pittodrie. Zander Diamond also netted as the Dons ran out 4-0 winners to earn their first opening day home win in 16 years.
McGhee said: "Paul's performance and leadership out there was invaluable. Having the luck to get three penalties and a hat-trick on his debut is the stuff that legends are made of. It was brilliant for us all to be part of that today."
And the Dons' manager believes there is no reason why the midfielder can't force his way back into the Scotland set-up if he continues to perform in the same manner.
"He knows he has to perform like that every week," said McGhee. "He will get tremendous confidence from what has happened today.
"The crowd and the players around him will also have tremendous confidence in him. If he stays healthy and we continue to improve then there is no reason why he can't work his way back into it."
McGhee, whose side finished a lowly ninth last term, was delighted with the free-flowing brand of football exhibited by his players.
He said: "It's not rocket science and I don't care what anybody said, I didn't suddenly become a bad manager after all the years I have been doing it.
"You need players that can change the game, you need pace in your team and we lacked that for so long last season. (Sone) Aluko, (Peter) Pawlett, (Chris) Maguire and (Josh) Magennis brought that today. Suddenly when you have that sort of energy and pace you have a chance.
"The basis of that team today was players that we have signed or that weren't fit for much of last season. Jerel Ifil was probably the only one that was there consistently last season.
"You don't know what to expect with a new team like that. You see things in training and pre-season that encourage you but you don't know what it is going to be like when you get to the serious business of league football. This result is something to build on."
Hamilton boss Billy Reid had no complaints about the performance of referee Dougie McDonald, despite the awarding of the three spot-kicks.
He said: "I thought the first two were stonewall penalties, the third one I would need to see again. I have no complaints at all and I thought the referee handled the situation well.
"It is a strange game as you can sometimes only concede a couple of penalties in a season, so to concede three in one game is quite incredible.
"All credit to Paul Hartley for scoring all three but you can't expect to defend like that and win the game. It was strange because I thought we played decent football at times and were the better team for the first 15 minutes but it was Aberdeen's day.
"Days like this happen in football and you just have to take your medicine."