Honestly, I was all hyped up for Brink before it came out. But after the demo was released, I lost faith in it. Mirror's Edge has better mobility than that game, and the customization is very shallow. I even checked out some reviews after the game hit shelves, and the majority of them (that I read) had the same feelings. Not saying it is a bad game, but personally, I wouldn't recommend it to anyone. The classes with specific roles? That's one great aspect of the game. With a little more customization options, an actual story for single player (not to mention better AI), and more variety in objectives, it could have been a great game! That's just me though
As for Deus Ex, I can't ever say that I've seen it as underrated. As mentioned above, it is a bestseller and probably will continue to be one amongst the few other bestsellers out there. The game is near perfect for what it is. Square Enix actually pulled a great game out of their money filled pockets!
Every one has their preferences

Let's all be receptive, respectable, and mature. Go Cohhilition!