So, I picked up Killer Instinct Definitive Edition not too long ago (after spending a few months playing the free version) and I have to say, it's rubbed off on me in a good way. The game is super versatile, allowing a person to play it like a normal fighting game (akin to Street Fighter) or play it like regular Killer Instinct. It has characters that range from being charge characters, to normal shotos, to primarily airborne characters to even a character who uses her own health to dish out insane damage. The music is fantastic and every character's theme fits them very well. The game itself isn't hard to learn how to get into at all. Having never played K.I. before, I did a few of the trials, picked a character to learn some moves with and thanks to the game's combo assist feature (which allows players to do simplified controls for combos) I began doing combos quickly. After turning combo assist off however, it seems like the game opens up a lot more since it allows for easier manuals (though keep in mind that may not be the case, and is only my mind perceiving it in that way) allowing for a more variety of moves for combos.
I guess what I'm getting at is are there any others who play the game, and if not, what are you waiting for? The free version comes with Jago (the Ryu of the game) and a free character that rotates every week. The Definitive is also $40 but comes with all the characters, retro costumes, Killer Instinct Classic 1 and 2, the soundtrack and a bunch of behind the scenes stuff for the game. So that's the best way to pick it up if the free version doesn't cut it for you.