Endless fun and a huge amount of content make this game one of the most complete experiences you'll find
In terms of gameplay it is almost identical to what you expect from a super smash bros game (if you have played a super smash bros game that is) which means that it is a lot of fun to play, all you need to do is hit your opponent until they are weak enough and send them flying out of the stage by a single blow. The roster of characters is one of the most crazy rosters you will ever find in any fighter game, and even so, the game feels extremely balanced, it doesn't matter what character you selected you can take down any other character as long as you know how to use your character.
One of the best additions to the super smash bros franchise is the online play, now, finally you can play online against other players and yes, you can play against unknown people so you are not limited to play only with your online friends.
Graphics are top-notch, the arenas are colorful, and feel alive, that's because there is always movement in them, for example in the Zelda wind waker arena you get to play in two moving ships in the middle of the sea, in the metal gear stage you get attacked by a metal gear from time to time. The characters from the game are extremely detailed and if you know the old characters from super smash bros you will quickly notice the graphic update they received from the previous game.
The music is probably the best you will find from Nintendo, and there's no other Nintendo game with better music than super smash bros brawl, more than 100 tracks were put in this game I am sure some of the tracks will bring you nostalgia if you have played Nintendo games through the years, some of the remixes from old songs like donkey kong country 2 bramble blast are worth mentioning since they are excellent.
So there it is, the only requirement you need to fulfill in order to enjoy this game is love having fun with videogames and since I think all gamers do then you should buy this game, it won't disappoint you