This game is the best of its kind. I've purchased it from 3 different storefronts. It's an amalgamation of 30 years of this relatively simple genre's evolution rolled into one product that keeps almost all the good design elements and scrubs almost all the bad ones. I'd say it takes a majority of its good features from Streets of Rage 3, with the speed and maneuverability and branching paths that Streets of Rage 4 lacks for some reason. There are nice unlockables acquired through just playing the game for a bit of time, and others that require you to meet certain challenges such as completing a survival gauntlet, a command training time trial, beating hard difficulties, and 1 credit clears. Considering that this is an indie game that was essentially a one-man team (plus a music composer), it puts most modern 2D games to shame. The only complaints I have are that there should have been a dedicated input for picking up objects (the punch button picks up everything), and co-op can only be played locally or through a desktop sharing application such as Parsec.
I couldn't find any reviews confirming if they had updated the game to the newer version with rollback netcode, so I took the plunge. Yes, this IS the Code Mystics updated release. The game itself hasn't really changed in nearly 20 years, but this is my favorite release of the King of Fighters. It is a "dream match" game and has almost every character the series had ever featured up until its release, and for some it might have even been their final appearance in an SNK game. I'm no expert on the balancing situation for this game, but the characters' movesets feel the most complete here. The Super Desperation Moves are a fun spectacle with some callbacks to previous arcs for older characters, and there's something that feels more charming about the pixelated sprites over what we have today. The only drawback to this game is that I feel like the backgrounds are a downgrade compared to the original KOF2002.
I couldn't find any reviews confirming if they had updated the game to the newer version with rollback netcode, so I took the plunge. Yes, this IS the Code Mystics updated release. Not much else to say other than that it's the classic KOF98UM. Hasn't really changed much in the last 20 years. If you like the NeoGeo era King of Fighters games then you will probably enjoy this one. In a way it's the first "modern" KOF as it introduced the Max Mode meter that most of the games have featured ever since. It displays the inactive characters in the teams standing in the background with cheering or defeated animations during the rounds, a nice detail that has unfortunately been lost in all the KOF entries made after this one.