The many options for customization and the depth of the gameplay keeps me coming back.
At first, I thought I would grow weary of this game pretty fast, as most multiplayer FPS's can't hold my attention for more than 20 hours because I feel like "I figured it out". This wasn't the case with MNC. Disregarding all the myriad of class options and customization (all, which I might add is available after the first hour of playing, not a bad thing) the depth of the game once you get to a certain level is very interesting and keeps me coming back.
Your goal isn't to kill other heroes, it is to get your bots to the other team's Moneyball to bring down its shields, at this point you can start working on destroying the Moneyball, however, if you don't damage the Moneyball for more than 15-30 seconds the shields are back up at full power. This allows teams to come back, and it happens alot. The matches are short, about 15 minutes, with a 3 minute overtime. Guys, I'm gonna stop blabbing, cuz now I wanna go play again, and try out a Tank with Lvl3 Reload Speed.