I have never really thought of Sunshine as a classic, it is still only one generation old. But as far as Mario games go, I never really play it much at all. Now the older ones, definitely. I still find myself playing Mario 2 and Mario World fairly often. I have always considered them both to be the best pick up and play games in the Mario series, at least for me they are. Mario 2 had my favorite gameplay so I still play it often even today. I thought it was just fun being able to jump on everything and any enemy can be used as a weapon against all other enemies. To me it was the Mario equivalent of a brawler, any and everything around you was a means of taking down enemies. I still wish Nintendo would bring back fryguy and mouser. And Mario World is large enough that I can wonder around and roam random areas for fun whenever I want to and still not clear it easily like most games I have played hundreds of time in the past. The game is so huge it will probably never get boring to play, all I need to do is just go to a different area for a shift in level style.
I would also love a remake of Mario Land 2 from the original B/W gameboy. It was a really fun game, loved the bunny ears powerup. Although it is a totally forgotten game today, it is incredibly hard to find anywhere. I wish I still had my copy from years ago.
So yes I do still play many of the classic Mario games, but there are plenty of NES and SNES games I will still play fairly often as I don't think I will ever get tired of them. Contra and Final Fantasy VI are two that I will probably continue to play for years to come.