At its simplest it's a game of puzzle-based boss fights and lonely exploration. It's a little odd at first because a lot of the normal gameplay/filler just isn't present. You find your Colossus, you have your boss fight and figure out how to defeat it. The exploration is present in the purest sense of the word; there's no mini games, no optional dungeons, no side quests. You explore to find the next Colossus, or just for the simple joy of seeing the world the devs have created.
Emotionally though, you're literally in an empty and forbidden land which means Agro becomes highly significant as your only companion. The fact that the devs made Agro control like a real horse adds to the emotional attachment. Then there's the expressions and actions of some of the Colossi that make you doubt your actions. Wander has a singular purpose in the game (hence the fact the game only really has boss fights), but the fact that these little nuances in some of the fights make you question his/your actions I think is quite significant.
Ok i might have to give it another chance eventually.
Xbox One, PS4 and Switch (+ Many Retro Consoles)
'When the people are being beaten with a stick, they are not much happier if it is called the people's stick'- Mikhail Bakunin
Prediction: Switch will sell better than Wii U Lifetime Sales by Jan 1st 2018