I do think that third party characters should not exist in Smash in the first place because I believe Smash should be and only be a Nintendo All-Star Fighter. But if they are to exist in SSB4 as proven by Megaman, then Sonic is the most worthy third-party character to be included, because I believe him to be more iconic and influential to Nintendo then even Megaman (yes, I said it). Snake, on the other hand, hasn't had nearly the amount of influence as Sonic or Megaman, and in recent years, his relevance to Nintendo is steeply declining. A Metal Gear Game did not even exist on Wii, and with MGS 5 not being developed for Wii U, perhaps a game of his will never exist on the platform. And plus, Kojima requested Snake after The Twin Snakes on Gamecube... at a time when Metal Gear's future on the Wii was uncertain. Now, Metal Gear has found it's home on other consoles, specifically Playstation. Bear in mind that I do love Snake as a character, it's just the fact that I don't find him as deserving as characters such as Ike, Lucario, Toon Link, etc. to make a comeback, because he isn't a Nintendo character and is not as meaningful as a his other third party counterparts, Sonic and Megaman.