Why stop there? Why not include every club that has spent any money at all? That would skew the answer even further in your favour.
Levy had more than 20 years to close the gap. How many years would you have given him before it became unreasonable to use Arsenal and Liverpool as examples of clubs that started with a significant head start? I'm going to include both because they're examples of clubs that have outperformed us without being financially doped.
Whether Levy did better than most other chairmen over the course of his tenure is beside the point (and, for the record, I don't agree that he did). The reality is that we've been in decline, by and large, for the past seven years. He doesn't get a lifetime pass because he performed well during the early and middle stages of his tenure.