A lot has been written on this already, you might want to spend a few days browsing forums...
- There is a fairly good correlation between pixel count and actual image detail when the sensors are used at their base ISO. At higher ISO, things become more complex, but the latest CMOS sensors appear to retain a better signal to noise ratio than CCDs,
- There are however some variations that mostly result from the use of more or less strong AA filters in front of the sensors. No AA filter means more detail, but also more moire,
- Image detail isn't the only important dimension of image quality. Dynamic range, shadow noise, highlight roll out,... are all critical as well,
- Selecting a camera based on the sensor technology it uses doesn't make a lot of sense IMHO. There are many varieties of CCDs, just like there are many varities of CMOS, signal treatment plays a huge role in final image quality,... the sensor is just one part of a complex system that should be evaluated as a whole only.