It's perhaps possible to give a rough idea of resolution at the centre of vision - corresponding to the anatomical structure known as the foveola.
It is this area that is responsible for the highest resolution images. At the foveola cone cells are densely packed - almost perfectly hexagonally close packed. The diameter of the cone receptors in this area is about 3µm and therefore each subtends approx 30 seconds of arc. Also in this area there is less low-level signal processing by the retina - there is almost a perfect 1-to-1 connection from receptor to nerve fibre leading to the brain.
What does this resolution mean? It means if you look at the full moon it's image will cover an area of the retina equal to approx 60 receptors in diameter.
As has been mentioned before, such precision is maintained only at the very centre of vision. As you move to the periphery, the receptors become larger, less tightly spaced, and more heavily interconnected. There is additional degradation because all the retina support structures (blood vessels, nerve connections) lie in front of the receptors, but are able to skirt around the outside of the very central part, leaving it a clear view. [*]
It's also worth noting that resolutions are not equal for different colours. Blue cones are relatively rare on the retina (accounting for only about 1-2% of cone receptors). There would, in fact, be little point in spacing them closer because the cornea and lens have significant chromatic aberration, which causes blue light to be poorly focussed onto the retina.
The other amazing thing about the eye is its dynamic range - which is simply extraordinary. A typical modern digicam sensor can distinguish about 3-4 log levels of intensity - and correct exposure with shutter and aperture adjustments is essential. The retina, by contrast, has over 10 log levels of dynamic range (although some time is required for it fully to adjust to an overall intensity). So not only, can it provide high detail, contrasty images even at high-noon on Miami beech or when skiiing, but when fully dark adapted has single photon detection capability.
[*] - you can see the main blood vessels in your eye with the following technique. Take piece of Al foil and punch a pinhole in the centre. Stare at a brightly illuminated featureless area (e.g. a wall or ceiling) and place the pinhole directly in front of your eye, so that you are looking through it. Now, very gently move the foil around.