United edged City 3-2 in a thriller at the Etihad.
When asked if he felt the Reds were worthy winners, Ferguson replied: "Absolutely. I think we played very well. I thought we were really fantastic today with some of our football and the game should have been out of sight in the second half with the number of chances we had.
"It's a funny game, football - it would have been 3-0 with a goal [by Ashley Young] that was perfectly onside. Instead they go up the park and score [to make it 2-1] within minutes. That's the kind of game football is, it can kick you in the teeth that way.
"I also thought we should have had a penalty kick because I thought Patrice Evra was brought down.
But there'll always be controversial decisions in a match like that because there are so many things happening."