Every game takes inspiration from something, and Fighting Games are no exception. Over the years, fighting game designers have not been shy about taking inspiration and even copying the aspects of other games in the genre. Sometimes, they even end up as better games than the ones they steal from.
Even some of the most influential Fighting Games, such as Street Fighter, took direct inspiration from predecessors. The basic concept of red and white gi-wearing fighters duking it out is adopted from the 1984 arcade game Karate Champ. Even the designs for the iconic characters Ryu and Sagat are based on characters from the manga Karate Baka Ichidai. As a result, fighting game designers and fans tend to view directly borrowing ideas from competing franchises as a form of acceptable homage, especially if the game turns out to be just as good, if not better.
Possibly the most influential rip-off in fighting game history are the various fighting game series made by SNK. Series like Fatal Fury, King of Fighters, and Art of Fighting were created as a direct result of Street Fighter 2's popularity. Two of Fatal Fury's designers were even former members of SF2's development team. As a result, many of the fundamental design decisions used in Capcom games like Street Fighter and Final Fight were implemented in SNK fighters. Things like the layout of the various meters (e.g. health-bars and the clock), the 2D perspective, motion inputs, and much more were all basic design choices that SNK borrowed from its competitors at Capcom. Designers would even poke fun at this fact over the years through characters like Dan Hibiki, who parodies SNK's Ryu clone, Ryo Sazaki.
Why Fighting Game Fans Love Good Rip-Offs
However, the SNK fighters were an exception to the general rule when it comes to fighting game rip-offs. There have always been, and always will be, a boundless number of poorly-made copycats. Few other series that took such heavy inspiration were able to reach the same level of quality, and the ones that did usually developed a unique style of their own. Games like Rivals of Aether, which took most of its game mechanics from Super Smash Bros. Melee managed to reach a similar level of quality while being remarkable in their own right.
Still, others go above and beyond and actually end up being better than their predecessors in some way. Skullgirls is an example of a fighting game that managed to surpass Marvel vs Capcom in many regards, even if it never reached the same level of popularity. While the game shared MvC's team-based system and fast-paced mechanics, Skullgirls' training mode and tutorial were far more detailed and helpful than MvC's combo challenges. Likewise, Skullgirls uses GGPO, a popular rollback netcode system, and has above average online gameplay as a result.
Despite the fact that some games manage to surpass their inspirations in some ways, few have ever managed to completely overshadow them. Fans of Fighting Games can be incredibly nostalgic, and will continue playing games decades after they come out. Even though it generally isn't considered a favorite among fans, the Street Fighter Alpha games are still being played. Quality matters to most players before everything else. So if a game won't boast total originality (which is extremely rare), it will still not stop them from being appreciated.