The Internet loves to discuss video games, so it's only natural that when 1UP.com sought out people from the gaming industry and the online community in general to discuss Mario, there would be much to say.  Everyone involved spoke up to say why they enjoy the Super Mario series so much and why they think it endures after so many years.  Read far enough into the article and you'll find a few thoughts from me regarding how all of these Mario games can co-exist without totally saturating the market:

"I started gaming with Mario and I still come back to Nintendo hardware to play the latest Mario titles, but I skip the releases that don't interest me. For instance, I couldn't get my hands on Super Mario Galaxy 2 quickly enough, but I didn't care to play Mario Sports Mix. More Mario is always fine with me so long as the quality doesn't suffer, and despite the rapid releases in the past few years, I think the series is doing fine overall. There's enough Mario for everyone in just about every genre. I think the trick is not to oversaturate any one genre at a time. New Super Mario Bros. 2, Paper Mario: Sticker Star, and Luigi's Mansion: Dark Moon are all on the way and since they're all different kinds of games, I don't see how they're stepping on each others' toes. Even New Super Mario Bros U seems to be just different enough from NSMB2 (GamePad emphasis, high definition visuals) to stand on its own feet."

I think that the best proof that the Mario franchise has lasted the test of time is that even after all these years, people still enjoy playing the games and discussing them.  There's a timeless quality to these titles, but they also have a way of bringing us back to the point in our lives in which we first played them.  I can't separate Super Mario World from the cold winter wind blowing through my open window on an overcast morning, nor can I break New Super Mario Bros. away from relaxing in a hotel room at E3 2006 with my Kombo pals at the end of a long day of work.  These games are locked into our lives and our memories, and with new players finding them all the time, I'm glad to know that new generations of fans will have their own stories to tell that are tied to the best that Mario has to offer.