Amorphous Ge/Si and crystalline Mo/V superlattices have been grown by dual-target d.c. magnetron sputtering with modulations according to finite approximants of various generalized Cantor sequences. The samples were investigated with both conventional powder X-ray diffractometry and high-resolution X-ray diffractometry as well as transmission electron microscopy. The experimental X-ray results were compared with derived analytical expressions for the locations and scalings of the diffraction peaks. Results from the X-ray measurements and the analytical expressions were also compared with numerical reflectivity simulations. The analytical and numerical calculations show good agreement with the experimental results.