I have no leg to stand on, since i'm american and have never made it over for a game. That being said, the atmosphere has gotten noticeably worse on the TV since city won the title in 2012. Maybe that euphoric moment ruined it for the short-term future. How can that drama ever be replicated? In that sense, I can empathize - for the short-term.
It's pretty evident on here that ticket prices have increased dramatically since that season. I can only imagine some fans are priced out, or have just decided its not worth it for the current prices. Again, it is easy to empathize with you all on that.
I don't know what the solution is, but it seems obvious to me that getting young people into games should be a top priority. The system isn't the same over here with university sports, but it is no coincidence that the best atmospheres are college (american) football games. My university has over 38,000 students packed into one side of the stadium. It is the largest student section in the country in a stadium that holds over 100k, so its not a fair comparison, but it is no wonder we are constantly one of the loudest stadiums in all of american sports. Student's get discounted pricing (of course which is subsidized my higher prices elsewhere in the stadium). There are guys that lead the chants from the field throughout the games. This video is from AFTER the game from a few weeks ago. It helps when you win, but there are usually that many people left after a loss. Win and lose, together (1:17 mark it gets good).
The "emptihad" jeer is a growing trend around the states. EVERYWHERE I go now, it is brought up when I mention I'm a city fan when I'm watching games at various bars. I have no retort. Games are quite, attendance is visibly low, and the stands appear half empty with 5 minutes to go. "Better beat the traffic, since the rest of my day is so damn important!"
I never complain about this on here because in some ways, I am part of the problem. One day I will make it over for a number of games, and then hopefully I can be part of the solution.