While premature, I would say that my controversial opinion (as I can tell just by reading this thread) is that Splatoon is the best game out this year but not for the usual reasoning one might apply to it like a meta score or hype factor or graphics or story. There are some very solid games out now for 2015, games much better rated, better looking, and better written than Splatoon by a wide shot, but they are largely what I would call as safe, aimed products, while Splatoon is an experiment.
The feel and impact, polish, sound design, and gameplay (and subjective fun) of it are simply unrivaled by current offerings, and as such even if the game is light on content, it is the better game. It is a game that I have found myself thinking about in the off-times, planning and plotting, and that's not something many games can make you do. The last game (that isn't Terra Battle) to wurm its way into my head like this was Dark Souls (Bayo/Bayo2 and now Witcher 3 (as it is the first Witcher game that I have found myself actually playing beyond the intro) are close but not quite there for me, and before that it was Halo and the Halo universe). Mechanics and feel are what make a game great to me (as well as being fun, obviously) and Splatoon offers that in spades (just the nuance of your ammo is you stealth is your sprint, has "wow"-ed me) as well as adding some color, life, and personality to my game time.
Its a game that sticks to you... like ink.
I haven't had this much fun with a shooter since the heydays of Halo with friends.