Ranking
The ranking shows only the data available at carranking.com.

Factors that affect test numbers includes air temperature, barometric pressure, condition of track surface, tune of test car.
Due to the different origins of the data, tests may not have been performed with the same conditions.

Acceleration
Significant difference: 0-60 mph, 0.3 sec. - 1/4 mile, 0.5 sec.

Top Speed
Typically as reported by the manufacturer.
Significant difference: 5 mph

Braking distances
Usually initiated when the pedal is touched, and just enough effort is used to avoid wheel locking; on cars equipped with anti-lock braking systems, the ABS is fully invoked. Significant difference: 60-0 mph, 10 ft.; 80-0 mph, 15 ft.

Handling is qualified two ways
Skidpad measures steady-speed cornering grip around a 200-ft. diameter circle (run both direction).
Slalom run through eight cones spaced at 100-ft. intervals, samples both controllability and grip during transient handling.
Significant difference: Skidpad, 0.02g; slalom, 1.0 mph.

Prices are estimated and might change per country or year.

Most of the definitions are from Road&Track magazine

Different factors can affect a car performance, such as: Air humidity, air temperature, barometric pressure, condition of track surface, tune of car. Therefore, you might have different performance data for the same car.

A good example is the Porsche 997 Carrera S (June 2007):

• Road&Track 0 to 60 mph is 3.9 seconds.
• Motor Trend 0 to 60 mph is 4.4 seconds.
• Porsche 0 to 60 mph is 4.6 seconds.

Not all cars have this huge difference of 0.7 seconds. According to Road&Track, 0.3 seconds difference is common for a 0 to 60 mph.

Here is Road&Track's explanation for the 997 Carrera S:

As you can see, creating a ranking for car performance is difficult with these kind of differences. Although, when we have enough data for a car, we are trying to use our best judgment to have an accurate ranking.