Some of you are being terribly patronising.
I don't understand the assertion that if it MK9 is not played regularly, it is not a legitimate choice to be your favorite title.
Final Fantasy X is in my top 5 games of all time. I loved the battle system, the characters, the settings, the boss fights and side games. Just because I don't play it all the time, it doesn't mean that it cannot be one of my favorite games. This is not a case of rose coloured glasses - whenever I play it, I still love it just as much.
Similarly, MK9 is one of my favorites of all time. I love the battle system, the roster, the backgrounds, the music, pulling off fun combos etc etc. Whenever I play it, I love it just as much.
MK11 is certainly more balanced and has less exploits, but for me, it is pretty boring and I don't play it much (I much prefer MKX). For me, the roster is terrible, the story and aesthetics are really lame, the playstyle is slow and boring, many of the characters seem incomplete, and it lacks hype.
People like games for different reasons. I don't think you should impose your opinions on others if they do not comply with your ideals of what makes a good game.