As has been widely reported across the web, DxOMark has put a Sensor Ranking page on their website, ranking the Sensors of most of the current DSLR's, which leads to the question "Just how important is the sensor?".
Let start with what makes a great picture? Simply put, a great picture invokes an emotional response in the viewer - the stronger the emotional response, the more memorable the picture. To do that, the subject of the picture needs to be compelling - either something unusual or different (in a good or bad way), or something taken from a fresh perspective (different angle, unusual lighting etc). Some of these elements are in the photographers control, for others being at the right place at the right time is more important than the gear you are using.
Assuming you are in the right place at the right time, light is co-operating, then just how important is the sensor?
The answer to that depends. If you are taking an action shot, then autofocus and metering are the most critical elements. If you are taking landscape or architectural shots, then you need detail, but have time to fine tune focus and metering, so the sharpness of the lens, and the resolution of the sensor are the most important. Having the right focal length to frame the shot is always critical. Having the right lens with a fast aperture and bokeh qualities to isolate the subject can be very important. If you are shooting in low light, then the sensors ISO is the most critical. Studio & Portrait - you want razor sharp eyes, but good skin tone and don't necessarily want to see every pore. Many people are currently complaining about wanting more dynamic range, but sometimes less dynamic range can make for a more dramatic shot. If you are using telephotos, reach and cropping ability may be critical, so the sensors pixel density is very important.
The bottom line is, the sensor is only one part of a much bigger equation, with the end result being the photograph. To capture the picture, you need to be in the right place at the right time, with the right lighting. Then to capture the image, you need a combination of lens, sensor, autofocus, metering (I've deliberately ignored white balance since if you are shooting RAW this can be adjusted in post processing) and so forth. Buying a camera purely based on sensor is clearly the wrong approach. However the sensor is a very important aspect of the camera to consider, which makes DxOMarks site an interesting read, when taken in the right context for what it is, and what it is not.
Here is the link: DxOMark Sensor