There're also four games before that (Hollow Fragment, Lost Song, Hollow Realization, and Fatal Bullet), plus a crossover game with Accel World.

Full disclosure, the games as a whole are generally the classic 3/5 "it's okay, only get it if you're a fan", but I've been an SAO fan since the original light novels (and, in my defense, I was younger and stupider at the time, but now I get to enjoy my trashy anime products with some well-worn, well-fitted nostalgia goggles), so I recommend checking them out if you just want more SAO-style anime silliness. Don't go into them expecting a great story, or super enticing content, or anything like that. It's pure fanservice (and with the amount of ahem DLC, it's fanservice in more or less every flavor) poured roughly into an RPG mold and allowed to cool in the blast chiller.