Mega Man III was on the cover and reviewed in the first issue of Nintendo Power I got (Vol. 20, Jan. 1991, because it came with a free copy of Dragon Warrior, sweet!), and it's my favourite Mega Man game. I find it funny that it's the Nintendo Power you looked at so often, too, Terra. Apparently it might be one of Revned's favourite Mega Man games as well, since it's one of the ones he did best in and the first he remapped, and I think the first he Mega Man game he even fully mapped, if memory serves (also note it was the first to be honoured as MotM).
Yet everywhere else on the Internet, people seem to prefer Mega Man II better. Indeed, it is really good too, and classic, and so very well-known (that was the first one I played, long before I played the first one).
I weep for Maxim, whose life experiences are deprived of true Mega Man action.
Though I do have to get over the fact that all the games I deem fundamental to play can't be expected to have been played by everyone who's a gamer. I've had so much difficulty convincing people that pre-VII Final Fantasy games or pre-Solid Metal Gear games even exist to "fans" of those series. >_< I imagine it'd be daunting to recommend Mega Man to someone who's never gotten into it, especially if they get turned off by all the various incarnations and spin-off series.
If you stick to the main series (including Mega Man & Bass), there's "only" ten.
I think some of those are redundant though, so I'd recommend Mega Man II and III at the bare minimum. >_>