Horlock and Barry are two of my all-time favourite City players. Underrated by non-blues, but I think most blues understand their value to us so I wouldn't include them here.
For 3 blues genuinely underrated by our fan base I'd pick:
Flitcroft - good all rounder flogged off in a panic by Ball towards the end of the 95/96 season to be spent on god only knows. Our midfield was woefully short for three years after
Distin - genuine class. Contribution overlooked as in a poor team (05-07) and next to fan fave Dunne. Then fans bizarrely turned against him for having the temerity to exercise his right to leave on a free after 5 years excellent service and be positive about his new club
Otamendi - yes, he could be rash and wasn't the greatest defender we've ever had. But definitely underrated by many fans; put in great shifts, was a warrior and scored some big goals. He played 34/38 games in our 100 point season, and 18 when we pipped scousers the year after (we had the best defence in the league over those two seasons, only conceding 50 goals in 76 games)...with some fans still labelling him 'sh*te'.
Bonus player: Phelan - underrated by me! Can't really say why on footballing terms as he was decent but I never liked him. Maybe it was because he cost so much, was a childhood red, replaced Dissa, or the fact he ran quicker backwards than forwards...but he was better than I gave him credit for.