In your opinion, what is the best 2d Fighting games series and why? Note: 2D!!! That means no Tekken, Soul Calibur, Dead or Alive, or Virtua Fighter. It also must be a series, meaning that it must include more than one game.
My vote: Street Fighter
The series that basically defined what we see as a fighting game, it features a myriad of infamous characters, attacks, and a fighting engine that is easy enough for noobs whilst still challenging and rewarding for true vets.