Brace yourself because this may be the most brilliant or the most stupid analysis of a GOTY contender thus far:
Stardew Valley: As soon as I heard the "It's Harvest moon", from everybody I was skeptical, but then I went to play and realize I loved the game, not ony it did everything it could to be different from the series I [kind of used to] love, but it did so many thing greatly, the Minecraft-style inventory and crafting, the bachelor system and the message of the achievements: do you go through the effort of gathering everything you need by planning ahead and working hard on it? Or do you let money solve your problems, basically recreating the routine you got away from to get a farm. So many things to do and so many mysteries to keep coming back to remembered me the reason I play video games for.
And now for the honorable mentions and other games worth mentioning:
Clash Royale: As much I hate the way the game cleverly dodges the pay-to-win criticism through clever manipulation, I have to admit, it's not a full cash-grab, (maybe 80-85%). Yeah, it's wait to get rewards, but it's surprisingly deep, the tower-defense, resource management hybrid really works, I tested various teams with the assets I had and when not trying to nickel and dime you, it's fun. But yeah, the horrible waiting times and the jewel system really turned me off.
Star Fox Zero: As much people harp on its controls, to which I'm not gonna defend, I liked the game, but since it doesn't have a alternate control scheme or a patch for it like Pikmin 3, I really hesitate to pick up and play again especially when I'm tired, but when I do, I go for it.
Mario & Luigi: Paper Jam - I think having two RPG series is taking its toll on both series, I still love the humor, the combat and the puzzle-platforming, but it really adds nothing new. If I have to pick one of the series for them to work full force on is Mario and Luigi because Bowser's Inside Story is one of my favorite RPGs of all time and Luigi is my favorite character (hence my love for Dream Team and Super Paper Mario).
The Witness: As a fan of Zero Escape and Professor Layton I was looking forward for this game, but as much as the puzzles initially grabbed my attention, I got really bored with it
MN9: sigh
Games I have yet to play to have any thoughts on: Salt and Sanctuary (single player mode with splitscreen co-op Dark Souls-esque action? count me in), Superhot (not a fan of shooters, but this one seems interesting), Kirby (a series that never falls on the "yet another X" category)