Take everything you know about Xbox Live Arcade games and throw it out the window.  Shadow Complex is a AAA quality game that is only available over Xbox Live.  In fact at just under a gigabyte in size Shadow Complex is more a digitally distributed game than an arcade title.  It just happens to be my opinion that Shadow Complex is the best game I've playing so far this year.

Shadow Complex is a side scrolling shooter/platformer game based on a novel by Orson Scott Card.  Two hikers accidentally stumble into an underground military complex and uncover a scheme to overthrow the government.  The game has you moving though out the base finding weapon upgrades and other accessories to help you traverse the 2D world.  You will have certain areas of the base unavailable to you until you've found certain weapon upgrades.  The game rewards those willing to spend time and explore the world with health, armor and ammo upgrades.

Shadow Complex is a full game that took me around nine hours to complete.  I only found 80% of the pickups and never got all the additional combat suit upgrades.  I found the story light but good enough to make we want to checkout the novel by Orson Scott Card.  The combat is fairly easy and the platforming puzzles are well balanced so you won't spend too  much time scratching you head wondering how to reach some point.  Often if you can't get to it, it's because you haven't gotten the upgrade needed.  I highly recommend this game because it is simply great fun to play.