These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
Broken Base: While many fans were elated to see Killer Instinct get a long overdue reboot, the fact that it's an Xbox ONE-exclusive titlenote which is justified, as Rare belongs to Microsoft now; but the fact that the Xbox One itself is a Base Breaker so far seems to have leaked over to the game too has many more split on whether it's worth the trade-off.
The game is adopting a free-to-play model and will release with only Jago as the selectable character at launch. This is itself a bag of controversy among players, especially considering each character will be $5.
This break has largely gone away with release; as it turns out, the pricing model doesn't try to pull any tricks to scam more money from the consumer after all and the free character rotates. About the only negative thing one can say is that the emulated, offline version of the first game isn't much of a bonus for the deluxe edition's extra price. It's largely been forgotten amid the microtransaction insanity of Forza 5 and Ryse.
The fact that Double Helix is making it, and they haven't had a very good track record...
Some people are disappointed by the fact that No Mercies and Ultimate Combos are not available at launch, since they consider them an important part of the game. Double Helix has stated that they will be added in the future, but that does not stop the disappointment.
First Installment Wins: In the eyes of many, KI1 is vastly superior to KI2 just by visual/audio presentation, including combo flashiness, with latter's gameplay improvements being disregarded since both games are not considered to be tournament worthy.
KI 2013 has a rare and amusing bug, where when a character is knocked out of their first lifebar, they will stay down and never get up. Since the timer doesn't run, there's no way to continue the fight, forcing either player to quit in an online battle, or to exit to the main menu in an offline versus battle.
Most Wonderful Sound: The announcer has a few. There's the classic "C-C-C-COMBO BREAKER!". The 2013 game adds "C-C-C-OUNTER BREAKER!" and "ULLLLLLLLLLTRAAAAAAAAAA!". The sheer enthusiasm the announcer has yelling them makes you feel awesome for pulling it off.
Nightmare Retardant: Fulgore is a big, hulking evil robot with glowy red eyes, long claws, and a multitude of deadly weapons at his disposal. He also makes elephant noises when you hit him.
Older Than They Think: The 2013 game's ability to chain together two Ultra Combos is new, but the hit count achievable with this was achievable without glitching in Killer Instinct 2.
Polished Port: Thanks to Nintendo having the programming team for the arcade version handle the Super Nintendo and Game Boy ports, instead of outsourcing it to a third-party developer. The result is that the SNES version was well-received and the GB version was surprisingly faithful, and more importantly, playable.
Rated M for Money - Fairly blatant at that. It was actually rated T, but the intent was still there.
Played Straight with the Xbox One release of Killer Instinct Classic, which has a M rating.
Replacement Scrappy: The newcomers from Killer Instinct 2 aren't too popular with the fans, being replacements of fan favorites Cinder, Thunder and Riptor.
Uncanny Valley: While the original game seems to hold up well enough, the character models for Killer Instinct 2 are very...off, especially by today's standards. Everybody (especially the women) looks like big-eyed mannequins with Frozen Face syndrome.