Physics limits the size of the pixel also and I think the limit is a bigger pixel then current lenses.
The diffraction limit with white normal light is something like
1600lp/mm / the F stop
So at F/1 1600 would be a perfect lens. I doubt this exists in anyplace.
At F/4 it would be 400 lp/mm. Supposedly some of the best 35mm lenses are already close to this limit.
A lab could test with monochromatic light and get higher numbers but that's not exactly usefull for most of us.
Now check your films. How many come close to even the F/8 number of 200 lp/mm?