By using total differential cross sections with resolved diffraction oscillations and absolute integral cross sections with glory oscillations, a new improved spherically averaged potential surface for Ne-CH4 is determined with a potential well depth of ε = 5.50 meV and a minimum distance of Rm = 3.78 Å. A slightly improved parameter set is also given for the isotropic Ar-CH4 interaction. By assuming the same realistic reduced potential form as was found for Ne-CH4 and Ar-CH4, the isotropic parts of the potential for Kr-CH4 and Xe-CH4 are obtained from absolute integral cross sections.