I've found the first copy of UK console mag Mean Machines from October 1990. They don't give a source for their charts. Presumably the Sega (Master System) and Nintendo (NES) charts are UK ones. Mega Drive charts could be either Japanese, US, or possibly even UK imports. It doesn't say which period the charts cover either, but probably September or August.
Actually Madden was pretty popular on Mega Drive in UK too, until EA released FIFA at least. Me and my friends used to play it all the time.







