Registered voters also favored the Boss over Zelda as well, so maybe they just really like MGS?
People on GameFAQs respect legacy and tradition, I think. Solid Snake is better than Zelda, both as a character and as an influence in gaming (not to be confused with Link) so I think that plays a part. However LOZ is just as influential so Zelda gets some of that respect too.
MGS is just kinda falling out of relevance. MGS4 was supposed to be the last game, and after 5 came out, and the way it was received... I think a lot of people were ready for MGS to be done. I love the series and I'm a diehard fan, but it is time to let Snake rest.
Snake hasnt been relevant since 2014. Add to the fact Kojoma leaving and Konami being asshats and BOTW influence yeah. Zelda still only won by a hairline.
If Kojima was still there and we got MGS6 with solid snake and not big boss then the match wouldnt be close. ---