The interpretive power of the newest generation of large-volume hydrodynamical simulations of galaxy formation rests upon their ability to reproduce the observed properties of galaxies . In this second paper in a series , we employ bulge+disc decompositions of realistic dust-free galaxy images from the Illustris simulation in a consistent comparison with galaxies from the Sloan Digital Sky Survey ( SDSS ) . Examining the size-luminosity relations of each sample , we find that galaxies in Illustris are roughly twice as large and 0.7 magnitudes brighter on average than galaxies in the SDSS . The trend of increasing slope and decreasing normalization of size-luminosity as a function of bulge-fraction is qualitatively similar to observations . However , the size-luminosity relations of Illustris galaxies are quantitatively distinguished by higher normalizations and smaller slopes than for real galaxies . We show that this result is linked to a significant deficit of bulge-dominated galaxies in Illustris relative to the SDSS at stellar masses \log \mathrm { M } _ { \star } / \mathrm { M } _ { \odot } \lesssim 11 . We investigate this deficit by comparing bulge fraction estimates derived from photometry and internal kinematics . We show that photometric bulge fractions are systematically lower than the kinematic fractions at low masses , but with increasingly good agreement as the stellar mass increases .