For the first Mario game, it's very good!
Each course is about the same length, and each should take about 5-10 minutes your first time (except for the very easy ones- those should take about one minute). In the game, you have power-ups which are the mushroom and the Fire Flower. When you obtain a mushroom, it will take two hits for an enemy to defeat you. With the Fire Flower, it takes three. Also good about the Fire Flower is that Mario gets fire powers, allowing him to hat the enemies before they even get to him.
The controls in the game are very basic. Use the C-Pad to move, the 1 button to run, and the 2 button to jump (I might have gotten 1 and 2 confused, sorry if I did).
The graphics in the game are not at all like todays games, and consist of 2-D, 8-bit graphics. I know what you're saying- "Well duh! The game came out for the NES!" Yeah, I was about to say that. Taking in to consideration that last comment, the game's sound is also obviously old-school, so don't expect something great.
The only real problem in this game is the no save feature, requiring you to restart the whole game if you die three times.
Overall, the game is a great buy. With excellent gameplay, great difficulty, and stunning graphics (that was completely a joke- lol) this game is a solid beginning to the Mario series.
For family friendly people, there's nothing in the game to be worried about, unless you consider jumping on mushrooms to be violent.