Chances are, most gamers nowadays may have heard of Undertale. After all, it won GameFAQs “greatest games of all time” contest and beat out games like Ocarina of Time and Final Fantasy VII. Some may argue that the victory doesn’t count because it most votes came from Tumblr users who don’t frequent GameFAQs, but it does not change the fact that it was always intended as a popularity contest and that every vote was from an individual who thought it deserved to win. So yes, it did in fact prove that Undertale is very highly regarded in the gaming community.
Keep in mind that this was all for a game created in Game Maker and that did not even have a press kit when IGN approached Toby Fox. So no this is not the same as some crap like game publications proclaiming a multi million dollar AAA title to be the Citizen Kane of gaming within a minute of putting the disk in the console. The only boost that Toby Fox got with Undertale was a successful Kickstarter campaign, and regardless of how one feels about Kickstarter, this shows how good it can be when used correctly.