For recent experimental results on thin superconductive films, the maximum average energy density as a macroscopic criterion of superconductivity is in better agreement with observed behavior than are any of the earlier criteria—maximum magnetic field, maximum current density, or maximum energy density. The earlier criteria are briefly reviewed, and characteristic formulas and critical curves are applied to an example for comparison with the proposed criterion. To determine the full significance of the proposed criterion, further experimental and theoretical work is needed.