I find it funny how some people complain about Bayonetta being a character from M rated games in Smash. I mean, it's not the first time it happened.
Both MGS and Bayonetta are games not quite meant for kids given their tone, themes and content.
Also, both Snake and Bayonetta were toned down in this game, so I don't see the big deal with them being from such kind of games. They fit in Smash, they're still in-character despite them being toned down and are fun additions to the roster that add to its diversity.
Well... Now that I think about it, it's kind of hilarious and amazing how there's content from mature games, to completely retro stuff such as Pac-Man and Duck Hunt, to casual games like Animal Crossing, Nintendogs and Wii Fit, to fantasy settings like Zelda and Fire Emblem, to sci-fi settings like Metroid and Star Fox, to video gaming long-running classics like Mario, Donkey Kong, Final Fantasy, Street Fighter and Pokémon...
All of it in one game. Many different facets of gaming, covering different genres, styles and eras. It's truly a sight to behold, no?