The resolution of the eye varies across the retina. Very high resolution is only achieved at a very small spot at the centre of the retina called the fovea, and maximum resolution only at the centre of that - the foveola.
At the foveola the cone photoreceptors are hexagonal close-packed and are approximately 30 arc seconds in diameter (the foveola itself is about 1 degree in diameter). This means that the centre of vision has approximately 10,000 photoreceptors. Again, at the foveola, each receptor has its own connection to the optic nerve and brain - so it would be reasonable to equate each photoreceptor in this area to a 'pixel' in camera parlance.
At progressively further from the centre of vision, the packing of the photoreceptors becomes less dense (the diameter of the cone photoreceptors increases to about 2 arc minutes in the periphery) and there is combination of the signals from multiple receptors (up to 100 photoreceptors may be combined into a single signal to the brain at the periphery).
There is another issue - there are 2 types of photoreceptor in the eye - colour specific low-sensitivity cones, and monochromatic high-sensitivity rods. At the fovea, it's pure cones - high resolution colour vision, but they require a high light intensity. Rods aren't colour sensitive, but are sensitive to low-light. However, in moderately bright lights (e.g. daylight, computer screen), they saturate and no longer produce useful information. These are mainly found at the periphery of vision - at the edge it's typically 1 cone to every 100 or 200 rods.
This is why central vision is very poor in the dark - there are no rods at the centre to pick up low levels of light.
There are about 7 million cones in the retina, and about 120 million rods. In terms of total number of signals coming from the retina it's probably around about 10 million. Although in daylight, the rods aren't producing any useful information, so you're down to about 7 'megapixels'.
The other interesting difference between rods and cones is speed - rods are much slower, taking up to 1/3 - 1/2 of a second to respond and recover. Cones are quicker, but their sensitivity to motion/flicker falls off sharply above 30 Hz.
Anecdote: I was walking across a park after dark, on clear night at approx half-moon (just below the threshold of cone vision). I checked my phone, which had a green LED display, and went to send a text message as I walked. The difference in response times between rods and cones meant that the bobbing movement appeared to be out of sync between the phone body and the screen, with the screen appearing outside the body on some occasions. It looked very strange and would probably have been quite disturbing if I didn't know why.
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