This game is more than just so. This is an experience... and this experience is truly reveling.
At first, it seems like a very normal 16bit game. The general premise is that you're a human that fell into the underground, a place filled with monsters. However, in the 2ND ROOM it already defies your expectations. How, I will not explain in respect for those who appreciate a true experience. However, I will say that it is very different from other RPGs in the sense that you are able to SPARE your enemies. To do so is your choice, but it will impact the game drastically.
Undertale about choice. Everything you do affects the world in some way or another, and you can end up with a different ending every time you play the game, even if you followed the exact same route. However, like I said before, this is not just a game. The characters feel ALIVE, designed absolutely perfectly to make every interaction as enjoyable as the last... well, almost. At other times, it can send a horrible chill down your spine... especially some of the egaster eggs...
This is an amazing game with an amazing story which goes even deeper than you could imagine. However, you must keep one thing in mind: Your antagonist has a special power... the same one you posses. If you use that power, you would not only destroy every creature in the underground, but the underground itself, as well as the fabric of reality that weaves it. And, although it may not seem tempting at first, do not let it fool you. Temptation will creep up on you, and you will be consumed by your curiosity if you do not keep it in check.
If you decide to get this game, follow this for the best experience:
Play the game ONCE (to completion), just like how you only live once.
Think of it as your LIFE... Do what YOU would do.
Engage with as many CHARACTERS as you can. Do not let a SINGLE ONE be forgotten.
Let the game CHALLENGE you. Frustration does not benefit you.
ENJOY EVERY MOMENT. If the game feels boring, you're playing it wrong.
In my honest opinion, Undertale deserves to be rated one of if not the BEST STORIES EVER WRITTEN. Although it has blown up massively, it is ultimately out-shined by AAA titles and is shoved back in favor of bigger game companies. The amount of joy put into my life as well as millions of people is indescribable, especially considering the developer team consisted of mainly 2 people.
This concludes my review. I hope I have inspired most of you reading to buy the game if you haven't already, and to thoroughly enjoy it.