MK9: 8 Took years for me to master stick again and completely start over from pad. Now advanced fundamentals... I STILL need to work on and I sometimes get lazy or tired but yeah 8. I've come a long way.
Injustice:0 never played to tough. Should've though.
All other fighting games: 6 If you play them all... You'll learn a ton of mechanics, skills, tech, schemes and philosophy's on fighting games in general the trick is applying as many/all to one game you love.
MKX: 0 I rather lose and learn then win and think I'm a good day 1 starter.