I realized recently that I've never actually played Super Mario Bros. to completion. Turns out it doesn't take very long to complete the game (just a couple hours), but those hours are super fun and rewarding all the same. We are all of course now very familiar with the formula of a Mario game. You run through levels and jump on the heads of your enemies, and eventually end up jumping on a flag pole to finish the level. There are 8 worlds, with 4-5 levels each, and the boss is very similar in each castle. The castles and boss fights get progressively harder, and sometimes you need luck or great reflexes to avoid falling into a pit of lava to your doom and having to start the entire thing over again. But once you complete a level, you definitely feel a sense of accomplishment at the end (especially the castles). Every time you complete a castle, however, Toad rudely informs you that the princess is in another castle and you have to continue searching for her because she's completely useless.
The world designs are still impressive even after all these years, with a great mix of land and water levels, often a combination of both. While the game is basic, the music is classic and sounds great to this day, and the difficulty spikes up appropriately as the game continues. While sometimes the difficulty and seemingly required luck to beat a level can be frustrating, the levels are so short that it doesn't take much away from the game to have to replay them several times.
It's a classic game that I still really enjoyed despite dozens of Mario games coming out after it, and it's a joy to play. While it's far from perfect, part of me feels that way inevitably because later Mario games drastically improved on its gameplay and without the original, we wouldn't have games like Super Mario 64 or Odyssey.