What’s your favorite fighting game series?

Street Fighter II (only the ones that ran on CPS1 hardware).

I've been playing it since 1992 and I've owned a Street Fighter II: The World Warrior arcade machine since 2007. I bought a new SNES in the early 1990s because I heard they were making an SFII port for it, and I bought the port as soon as it came out, for something like $60 (which, to this day, is still the most I've ever paid for a video game, not counting actual arcade machines).

I wasn't disappointed; it was the best arcade port for a console I'd ever played. There were some minor differences, but my skills from the arcade worked perfectly fine without having to make any adjustments to the way I played the game. Prior to the "16-bit" era, arcade ports with that level of fidelity were unheard of.