Another argument for Snake: As many might know, arguments involve him not being a Nintendo character and how he's hardly had any games on Nintendo consoles. Super Smash Bros. Melee could have had Snake at the time, but he barely missed the deadline for what characters could be in. To think that Sakurai would even put Snake in Melee (despite Twin Snakes not even released or, as far as I'm aware, even in development) would boggle the minds of many. At the time, we would've only had what, the port of Metal Gear to the NES, a non-canon sequel not even official, and Ghost Babel which also isn't canon? You see where I'm going at?
And also, we haven't seen the back of the box for the new smash. I thought this was strange, I'm not sure why, but it makes a lot of sense if Snake is back.