Nintendo's most popular (and only!) fighting franchise started off quite strangely - in fact, it originally didn't even have any existing Nintendo characters! Created by Kirby Creator Masahiro Sakurai of HAL Laboratory and Satoru Iwata, the game was originally called Dragon King: The Fighting Game, and featured fairly featureless blocky figures duking it out with each other. Sakurai suggested using Nintendo characters instead to give the game more character, something he felt was necessary for a home console fighting game. Nintendo approved the idea, and Super Smash Bros. was born!
Even though the franchise has only had three games, it's hard to imagine there being even a single Nintendo fan who hasn't played one of them. All three games were some of the best-selling games on their respective systems, and the series has a massive fan following.
The gameplay in the original Super Smash Bros. is the same as its sequels: you run around on a 2D stage with up to three opponents, attacking each other with melee attacks and items to increase their damage percentage, which can be seen at the bottom of the screen. The higher this percentage is, the further opponents fly when you hit them with more powerful attacks - if an opponent flies off the screen in any direction, he loses a life and you gain a point.
It should be no surprise that the original game is fairly bare-bones when compared to its successors in terms of content. Once everything has been unlocked, there are only 12 selectable characters to fight with and 9 stages to fight on. If you've played Melee (26 characters and 29 stages) or Brawl (35 characters and 41 stages) before playing the original then this will no doubt feel like a massive step down.
There aren't that many things to do in the game either. Melee and Brawl feature a "Classic" mode, an adventure mode, multiplayer, minigames such as target tests and a homerun contest, collectable trophies and more. In the original, however, you'll only find a multiplayer mode and a single player mode, in which you tackle a bunch of computer-controlled opponents, beat some minigames and defeat Master Hand, the game's final boss.
Melee and Brawl both have you unlocking things weeks or months after you first play them: here, however, you're likely to have everything in a day or two. While that's nice for the game's multiplayer aspect, meaning you and your friends can quickly use whichever character they want, it does feel like you're "done" with the game rather fast.
Super Smash Bros. was no doubt a fantastic game when it first came out. Having various Nintendo characters fight against each other was any Nintendo fan's dream, and it finally allowed us to do just that. In the decade since its release however, it's had two sequels, and these improve on the original game so drastically that it's really kind of hard to recommend it to anybody who's played the later games.
The only real reasons to download it are out of nostalgia, or if you've never played a Super Smash Bros. game and simply want to start from the beginning. It's still a good game, it just feels incredibly basic after its two jam-packed sequels.