What is "really good" is subjective. However, I'll just throw out a few stats out there that might highlight Kolarov's goal and assist record and how it far more closely matches effective attacking players than Clichy's does.
Silva
12/13: 37 starts, 5 goals, 11 assists
11/12: 47 starts, 8 goals, 19 assists
10/11: 43 starts, 6 goals, 13 assists
TOTAL: 127 starts, 19 goals, 43 assists
= 1.95 starts per goal/assist (last two seasons)
= 2.04 starts per goal/assist (City career)
Kolarov
12/13: 17 starts, 4 goals, 3 assists
11/12: 21 starts, 4 goals, 6 assists
10/11: 31 starts, 3 goals, 2 assists
TOTAL: 69 starts, 11 goals, 11 assists
= 2.23 starts per goal/assist (last two seasons)
= 3.13 starts per goal/assist (City career)
Clichy
12/13: 33 starts, 2 assists
11/12: 37 starts, 4 assists
TOTAL: 70 starts, 6 assists
= 11.67 starts per goal/assist (last two seasons/City career)
Kolarov's goal and assist record ain't have bad when you compare it to Silva's and there's a ocean-sized gap between Kolarov's and Clichy's goal and assist record. I'd say the evidence supports the idea that Kolarov is effective going forward. If it's a matter of relativity, and Kolarov is 'ordinary', then Clichy is horrifically bad considering he's 5.23 times less likely to bag a goal or assist than Kolarov is.