best game ever poll was just a popularity contest. it makes sense that undertale would win because it came out like two minutes ago and people are pooping their pants about it, and has a more active current following.
now, if you asked me right now if i thought undertale were better than any of the games it went against, i would absolutely say "yeah." to what degree is that novelty, and to what degree is it genuine admiration? hard to tell. but i bet you nobody actually changed their opinion or voted against their gut just because some guy on the internet told them their opinion was irrelevant or invalid. maybe they did it out of spite, maybe they did it as a settlement, but you don't typically just change people's preferences by saying "we deserve this!!!!!!!!!!!!!!!!"