The King of Fighters has always been among the underdog fighting game series compared to its peers like Street Fighter and Mortal Kombat. Whether it be due to its stubbornness to stick on the Neo Geo arcade machine architecture until 2003, the usage of 24-bit graphic sprites until its twelfth numerical entry in the series, or the stronger anime influence on the series than the genre's most famous franchises, The King of Fighters is a series that is highly underrated and deserves much more praise than it gets.
Whereas the series is notable for experimenting with new gameplay engine mechanics, The King of Fighters XIII opts to lift the most popular gameplay elements from the fan favorite entries, The King of Fighters '98 and The King of Fighter 2002, and marries them to the high quality sprite designs introduced with The King of Fighters XII, making for one of the greatest entries in the series. The game's 36 character roster hosts all the franchise staple characters and a good amount of fan favorites, which provide a large amount of variety in character playstyles to choose from so you are bound to find a character that will suit any style of player. The game also sports one the most robust amount of options seen in a 2-D fighting game ranging from an in-depth tutorial, arcade mode, story mode, challenge modes, online multiplayer, and even a custom character color editor for personalizing your favorite characters.
What makes Steam Edition different from the console version of the game is that it includes the three DLC characters into the base package and sports the refined balancing from Japanese arcade only revision of the game "The King of Fighters XIII Climax". Also, while the netcode is vastly improved over its console counterpart, the features present for online multiplayer are the same. The game does not feature any sort of lobby system nor does it allow you to browse replays or spectate other players matches. These aren't really a deal breaker but the lack of them is a real shame.
If you are looking for a game in the series for a good first impression or are just looking for one of the fighting game greats from the seventh console generation of games, you cannot do very much better than The King of Fighters XIII Steam Edition.