Barry was underrated by the general football sheep, but I don't think any City fan thought he was anything short of top class. He got scapegoated for England losing to Germany, despite being visibly unfit and being massively let down by teammates who were only out for themselves, and his reputation with the non-City public never recovered. It was a sign of just how important he was that he was forced to play despite being in no fit shape to do so. Englands only actual holding midfield player that I can think of, I'd probably still have him in my starting england team now, even though he's completely past it.
De Jong on the other hand I think was hugely overrated, however much I loved him. He was a flashy player, which is odd for a holding midfielder who doesn't do much. But because he threw himself into sliding tackles at every opportunity, he got your attention and it made him seem like he was doing a lot more than he actually was. We were probably a lot better when he wasn't in the team. I'd put him up there with the Bellamy's and Milners, players who are pretty average but you always like watching as they look like they are trying and they catch your eye with their energetic style of play