O'Neill told the club's official web site: "It was a great game. We scored four goals and we were brilliant going forward - an absolute dream.
"Gabby scored a hat-trick and it was as good a hat-trick as you're likely to see. All in all we were absolutely magnificent.
"We had a few scary moments towards the end when it had looked pretty comfortable. But we full deserved to win the game.
"I felt it was an enthralling game. The action was end to end and Manchester City played their part in a brilliant entertaining game."
The Irishman added: "There were no goals in the first-half but at half-time I felt we were doing fine. We could have scored maybe early on but it was just a matter of players getting to know each other.
"But at half-time I felt, whatever we do, don't throw it away. We had to keep our shape and keep our discipline.
"Then we got a goal just after half-time and that set us up nicely. They got the equalising goal, much to our own fault, but the fact is that we came back again.
"We came back in phenomenal fashion and I think the crowd will be delighted with the performance."