The first time I played Super Mario Bros 3 was the NES version in around 2006-2007 on a site called Nintendo8.com which is a site that lets you play NES, SNES and loads more titles for free. The next time that I played it was in Christmas 2010 on the Super Mario All-Stars 25th Anniversary Collection. I also watched the Super Mario Bros 3 cartoon a lot and I played Super Mario Advance 4 on My Boy as well, so I had quite a history with this game.
Super Mario Bros 3 is by far one of my favourite Mario games of all time. From the power-ups to the Worlds and even the platforming, Super Mario Bros 3 showed major improvements from the other Mario games which makes the game a stand out title for the NES as well as a classic for older gamers. Super Mario Bros 3 has been a favourite for me as it had a lot of unique features to the game like the Warp Whistle which sends you to the Warp Zone, the many secrets you can find in the game, the wacky power-ups like the Kuribo's Shoe and the Tanooki Suit, the challenging levels and more, Super Mario Bros 3 had everything a Mario fan and a gamer would truly want in a platformer game.
If you haven't played this game yet, I suggest you should because it is available on different platforms like Wii (VC and All-Stars), 3DS (VC), GBA, SNES (All-Stars), Wii U and you can buy a cheap copy of the NES version on shopping sites.
Here is a link to Nintendo8, the site I was talking about earlier: http://nintendo8.com/