This is the kind of game that everyone can and should play. It's such a unique experience, crafted lovingly by an extremely talented person. The attention to detail is insane - Toby thought of EVERYTHING you might conceivably think to do in the game, and quite a few things you likely wouldn't. It feels like every time I open Undertale to play it, even after having getting many of the different endings, I learn something new about the game.
It's amazing how much this game can make you feel - whether those feels are sadness at parting from a character you came to love, or laughing at the humor in the game, or genuine guilt for killing someone. Similarly, the soundtrack is some of the best in video game history.
There's not much I can say that hasn't been said already. But this game will go down as a classic for decades to come.