Super Mario Bros 3.

While SMWorld expanded quite a bit on the formula (new powerups, Yoshi, Switches, Star Road...), SMB3 did all the groundwork and Nintendo only expanded on it with World. SMW is just evolutionary, while SMB3 was revolutionary.

True and mario 3 had better platforming as well.

Nothing beats the original Super Mario Bros

Mario Bros 3 has long been my pick, with World a close second, but Wonder is a real challenger to this established order for me; I'm still not sure where exactly it falls, but it definitely rivals World for the #2 spot.
It may not be as groundbreaking as Bros 3/World, but the sheer creativity of its gameplay design is off the charts.

I constantly waver between Mario World and Mario 3, as they're both the pinnacle of the series and both excel in distinct ways. I think looking back now, Mario 3 is the overall more enjoyable, more well-crafted and imaginative game. Mario World I will give the edge when it comes to accessibility, and its dynamic map screen.. and of course Yoshi! But as a *whole* I still think Mario 3 edges it out.

Yoshi’s Island(??). And adding Mario Wonder just feels a bit unfair. That game had twenty extra years over it’s most recent competitor (plus recency bias).

I'm surprised by the lack of any New Super Mario Bros. games. I think the NDS original and NSMBU Deluxe are a lot better than SMB3 and World...

I haven't played Wonder yet (it's probably next out of my backlog), but of the ones I have played, it'd probably be:

SMB3>World>SMB>SMB2>NSMBU>NSMBWii

Granted, I grew up with the older ones so I prefer them (SMB3 is my favorite game of all time), but the New SMB games were fun as well. Every single one of those games I ranked were included in my all-time Top 50 list from the VGC Greatest Games event.

Those ones rarely get many votes in similar polls I've seen, and polls here on VGChartz only allow so many options so I had to prioritize and list a lot under "other".

Recency bias is kinda balanced out by older games having the advantage of nostalgia. 

I enjoyed New Super Mario Bros. Wii and New Super Mario Bros. and Luigi U too.

Yeah, the "New" style was getting boring at the U time, but at least they made some cool games before moving to a new style.