It is not only that
City's points
08/09 20.0000 EL - Quarter Final
09/10 3.5856 no participation
10/11 16.6714 EL - Final of 16
11/12 20.0500 CL - 3rd Group stage, EL - Final of 16
12/13 10.2856 CL - 4th Group stage
sum 70.592
16.592 are points you have because of the performance of the English clubs
Celtic's points
08/09 7.3750 CL - 4th Group stage with 5 points
09/10 5.5332 EL - 3rd Group stage with 6 points
10/11 2.2200 Out in EL playoffs
11/12 5.5500 EL - 3rd Group stage with 6 points
12/13 16.8600 CL - Final of 16
sum 37.538
3.038 are points they have for the performance of Scotish clubs
You see the difference. 13 points are because of the country coefficent.
You have done better than Celtic... (apart from last season)