Combination of little time, money (to go to the arcade), and honestly a lack of effort. I realized at some point that I expected myself to lose every match I played and since then I barely cared about learning new things or trying to win. At the time winning was the exception for me, not the rule. And that's my fault, I tend to give up easily on a lot of things if they don't go my way fast enough. And Dark Souls 2 (and soon to be, Final Fantasy X HD)
I've been on a long hiatus, but I want to give Street Fighter a try. I played Marvel too much to be at the point I'm at now, which I feel isn't good enough. I want to try starting from scratch again eventually.
Amazing game, but maybe not for me. Like I said, Marvel was my first, and I had no idea what I was doing. Hopefully I can apply what I learned from it to other games, playing Marvel was a huge lesson in humility to me, and I'm happy I played it.