In another time, I'd buy your argument.
In this day and age though, with the likes of super-rehash queens Playmore milking SNK's legacy for all it's worth, and Capcom pushing out turds like CFJ/CFE, I think Cave deserves the crown. Cave may stick to a formula, but they make the finest damn shooters on Earth now, and every one of their shooters has something different and unique, and every game they make is fun and well crafted. Capcom and SNK brought out title after title in the exact same genre in the 90s, but they deserved respect because they were giving fans what they want and the games showed some genuine effort.
KoF-SamSho-RealBout-FF
SF-SFZ-Vampire-SFIII
ESPG-Mushi-Ibara
Same school of thought, different genre. Hell, I'd argue now that what Cave does is that much more precious, since damn near no one makes 2D games at all anymore.