Whether it's good mileage or not depends on a number of variables. For example, is it a four or six cylinder? What's your mix of driving? Lots of idling, stop-and-go traffic or relatively uninterrupted highway miles at a relatively constant speed? How are the tires? (Tires can have an effect on mileage). Lots of hills in the area (SF, the Ozarks, Cincinnati, etc.)? 

Modern cars insulate drivers from recognizing emerging problems via computer correction. (For example, computer-adjusted increased duty cycles on coils make up for deteriorating spark plugs that have increasing gaps, without any apparent change in driveability. The same thing goes for computer adjustments to a throttle body that is carboned up). Some small loss of MPG can, at times, be the trade-off for the insulated experience. 

Probably the best simple (and only partial) indicator of efficiency is to scan for the Long Term Fuel Trim (LTFT) numbers. It takes some pretty skewed trims (usually around 25 percent) to set off a check engine light. If the vehicle's LTFT is over 10 percent, plus or minus, you might want to investigate a bit further. 

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By way of reference, for my 4 cylinder, 2008 Camry LE with 154K: Generally, my combined mileage (hwy and city) is around 25 mpg, in Central Texas. When I'm up in Chicago, during most Spring visits, well, there's a ton of traffic lights and stop-and-go traffic. I average about 19 mpg up in Cook County. On the Interstates and toll roads up from Central Texas, I generally average around 28 mpg, which is pretty close to EPA figures. So, mileage will and certainly does vary. 

sounds like good mileage to me.

You know the numbers they put on the sticker are lies, right?

20+MPG on a 8, almost 9 year old car? sounds O K to me.

Learn to coast up to lights and down hills and try not to run over 2000 RPM and your MPG will improve.