I've thought this for about a year now but have never really been arsed enough to comment on here (mostly because any criticism of Kompany would've been treated as blasphemy in the past). He WAS great in the past (under Mancini), but...
I genuinely don't think I've seen a more overrated player at the club in my life (22 years). Now this doesn't mean he isn't still a very good player, it means he isn't anywhere near the great CB's of the game that people seem to compare him to.
Always running out of position, always picking up stupid bookings for daft challenges, always lapsing in concentration, doesn't read the game particularly well and far too error prone (even more so recently). All key things that a top CB SHOULDN'T be. As a CB, if you consistently make that many mistakes then you're not reliable which simply means you aren't that good.
His only 2 genuinely world class seasons were under Mancini for my money. Looked shaky as fuck since, Demichelis has been better than him for the best part of a year. It's not just our own fans, seems like some pundits see him as some sort of Maldini level player. Baffles me. I think a lot of people rate him based on athleticism and the tackles he will sometimes win where he breaks out from the back 4.
As I said, I've thought this about Kompany for a while, nothing knee-jerk about it.