Just because you aren't a fan doesn't mean he isn't a legend. Snake is an incredibly iconic video game character whether you want to admit it or not. If you want to talk sales, MGS has sold more than Mega Man has. Metal Gear Solid is a revolutionary series for the stealth genre of games, that much is undeniable. Also, I find the statement, "His game series is the legend, not him as a character" is silly. When you think Metal Gear Solid, you think Snake. The main protagonist. The gruff voice that has permeated the entire series. The guy who is there in every game of the series, whether Solid Snake or Big Boss (Naked Snake). He brings the character to the series.
A difference between Snake and Lara Croft is that Snake has already been in Smash Bros. He's already proved himself to be a unique character that has a Smash fanbase. Both are certainly iconic characters, and I would go as far to say they're both video gaming legends.
Sure, Snake got in because Kojima wanted a favor. Big whoop. Snake turned out to be one of the most unique characters in Smash Bros. as a series.
It's one thing to not like a character. But to say that the character isn't a legend because of that is just silly.