Mirror's Edge is widely considered a very ambitious and creative game. Despite this, the risks it took proved to have great consequences when the game did not sell desirably. President of EA Games Frank Gibeau addresses the game's shortcomings, citing its polish and execution as two vital reasons behind its unimpressive sales:

What I learned from Mirror’s Edge is that you have to execute, you have to spend more time on a game to ensure it’s polished, and you need to have the depth and persistence of an online game. First-person parkour across buildings is fun, but to be blunt, Mirror’s Edge’s’ execution fell short. There were issues with the learning curve, the difficulty, the narrative, and then there was no multiplayer either. The key learning from us was that if you’re going to be bold with that kind of concept, you need to take it as far as it can go in development.

While I won't disagree with all the points he formed, I have to say, cut the game some slack. The general gaming community knows that sales are hardly an indicator of quality, and this is true especially for gems like Mirror's Edge. If you've never played Mirror's Edge, find out why you absolutely have to.

[Develop]