This one wasn't a hard one to figure out. Super Mario Bros 3 is platforming goodness, and I bet you couldn't find a legitimate top NES list without it in somewhere in the top ten.
Super Mario Bros. was a compelete step up over Donkey Kong and Mario Bros. Super Mario Bros 3. had evolved so much over 1,2, and Lost Levels. The world was so much diverse, more paths to take, more secrets involved, and a much tougher challenge. Just hope your friend who played along with you didn't take advantage of every stupid mushroom house because he's a greedy jerk.
I think my favorite memory of SMB3 was getting to big world-small world. A rather gimmicky idea today, but back then it was like breaking the fourth wall. You almost couldn't believe what you were seeing.
Even though I very much prefer the All-Stars version pictured above, the NES original is still a classic even though the SNES version has a much prettier coat of paint. Most of these games on my list are older than I am, and they still hold up as well as they did in the 80's and 90's. Good games don't age, mediocre games just lose their luster. And Super Mario Bros. 3 is as perfect today as it was all those years ago.