Explanations / Notes:
"System" can mean an individual system, a hardware family (DS counting for all the different models), or manufacturer (Nintendo, Sony).
Media Create numbers don't start until 2003, so for systems that released before then Famitsu is the way to go. PS2, GBA, GCN, and Xbox are the biggies of that time frame.
The generic Versus was based off the PS3/Wii version, so it shows what it would take for "System 1" to catch up to "System 2" rather than the other way around. You can input the systems in the other order and the calculations will be legit, but it will seem pretty strange.