It's supposed to prove that Snake can look decisively stronger than an elite Nintendo character going in and then have his Smash strength sapped to lose 'badly'. If Samus can do it, why couldn't Mario?
Good thing I'm not talking about Mario/Snake directly! Don't have to worry about Brawl SFF if we're talking about indirect value. (and hey, Samus/Snake is another candidate for rSFF, though I don't find this one convincing at all)
--
2002 Link, 2003 Cloud, 2004 Link, 2005 Link, 2006 Link, 2008 Link, 2010 Link, 2011 Cloud.
Link 6, Cloud 2