Lately I got many links to new projects of camera databases. So here is a list of link you may find useful to learn more about the existent cameras and lenses:
Digicamdb.com: Easily find sensor size, pixel pitch and other important sensor characteristics for 3284 digital cameras.
Mirrorlessdb.com: Full specs of all mirrorless cameras and lenses.
Lesnumeriques: A french camera studio image comparison.
Google docs file: Mirrorless Camera Native Lenses