I enjoy playing Super Mario Bros. on my Nintendo DS unit. It's a great game for young and old alike. There are different levels you can attain (I'm not even sure how many because I haven't gotten very far in the game yet), and Mario has to face an assortment of different obstacles in order to get to another level. The video and audio quality I have found to be great on this game. It is very entertaining.
Another thing I like about Super Mario Bros. is the assortment of mini games you can also play. That way, if you get tired of trying to progress Mario through his obstacles, you can give yourself a rest by playing one of the mini games, which are also very entertaining. Let's face it, I'm a big kid at heart, and I enjoy playing these games when I have some free time (which, unfortunately, isn't often enough).
I recommend Super Mario Bros. for young and old alike.