If you combined Super Metroid with Uncharted, this game would be the result. One of the best games ever. Period.
The game starts off as you and your girlfriend are backpacking near a lake. All of the sudden, your girlfriend disappears and your initial search for her leads to the discovery of a plot to take over the world by an evil organization. During your journey to rescue your girl and defeat the bad guys, you constantly find items, weapons and upgrades that either make you stronger or allow you to reach previously inaccessible areas. For example, you start out with a flash light and continuously find bigger and better guns as you progress. Additionally, you will obtain various pieces to a powerful suit that allows you to double jump, run through barriers, and generally take more damage as time goes on. By the end of the game, you will ultimately be an armored soldier with the tools to take on an army by yourself.
The game gives players the latitude to explore as they so choose, but it also provides a map with a blue line that show each player the next objective and essentially, where to go next. So, if you're like me, you'll appreciate the direct nature of the game as it points you in the right direction and leaves little need for an extensive hard-copy guide.
The combat in the game is two fold: players can either use the weapon they possess at the moment or take each enemy out through hand-to-hand close quarters combat. Using your pistol, rifle or shotgun will allow you to kill the enemy at a distance, but a hand-to-hand kill may allow you to silently defeat an enemy without alarming many others. The game leaves the strategy up to the player and rewards you for increase numbers of head shots, "make-em scream" kills and so-on.
The boss battles in Shadow Complex are fantastic and will challenge players without feeling impossible. The further you go, the harder the bosses become, of course and the more you will have to use your smarts as much as your weaponry. The ultimate boss battle(s) happen at the end in a frenzy that I'm not going to spoil but thoroughly enjoyed. You have to see it for yourself.
In conclusion, Shadow Complex brings is a conglomeration of action, adventure, discovery, upgrading, heavy weapon usage and hand-to-hand combat that gives players a reason to play a stellar 2D adventure time and time again. It is one of the best games...if not the best game...ever produced on any system. Without a doubt, a 10.