I'll add all the games that are in the Super Mario series article in the wiki. I'll start with the Mario Bros. series, then there'll be the main series with other games scattered around and then there'll be reissues. Then there'll be the Wario Land series and the Yoshi's Island series. And in the end there will be Luigi Bros.. Then there's the Super Mario 64 series that's not what you think. The one that says "Famicom Mini: Super Mario Bros. The" is a port of SMBTLL that I couldn't write the name right.
For me out of the main series it's Mario 3 or Mario World. It's hard to pick between them, because depending on the day I could go either way. Honorable mention to Mario 64 although it's not as timeless as the other two.
