The characters that you were able to enjoy for each of the versions of Super Smash Bros include Yoshi, Samus, Pikachu, Mario, Luigi, Link, Kirby, JigglyPuff, Fox, Donkey Kong and Captain Falcon. Since the original version was released back in 1999, there have been many characters brought into the game from many different game titles.
Most of them are well known, but there are a few that are very obscure and you would have to be a major gamer to have even heard of them. Characters from games like Mario, or Ice Climber might be more well known than ones from EarthBound/Mother and Game & Watch. Most of the sources that are posting online about Super Smash Bros agree that there will be plenty more in the future.
The franchises that the characters are coming from have made the Nintendo name even bigger over the last fifteen years and there is no reason to stop that as long as the gamers are willing to put their money on the table for the newest game.