Shadow Complex (XBLA):
An excellent Metroidvania-style game in a pretty generic "secret army base." The plot is based off of an Orson Scott Card series of novels, which, after my experience with his Ender's Shadow series, are probably a 50-50 mix of intriguing political thriller and ZOMG HAVE BABIES WOMEN ARE BABY FACTORIES.
Now, it is with a heavy heart that I say I'm finished with this game, but I literally have 100% complete on it. In true Metroidvania style, you begin the game with nothing but a flashlight and a backpack and eventually can become a nearly-invincible one-person-army in 12-15 hours. The game is built on the Unreal Engine, so although it's only a 2D side-scroller, you can fire at things in 3D and aim with the right thumbstick.
Combat is varied enough to keep me interested through the whole game. Your first gun is a pistol, which gets upgraded to a submachine gun, then an assault rifle, etc., etc., and you can always pick off foes at a distance. The subweapons are different enough to be useful in different scenarios-grenades, missiles, and foam grenades are all more effective against certain enemies than the regular gun. My personal favorite is the melee kill, especially from stealth. If you can get up close to a normal guard, you can snap his neck/kick him off a ledge/suplex him. After an armor upgrade, you can even do that to the giant guards with missile launchers, and punch dudes into the next state. If you perform the melee attack quietly enough, you can make your way through groups of guards like a ninja. Sure, it's been done before, but it's still a blast.
Exploration is relatively smooth, since your character's early Climbing Gear allows you to hang on to walls briefly (Mega Man X style) and wall jump. After a few mobility upgrades, vertical climbs become a non-issue, and only one or two power-ups involve frustrating...er, challenging jumping puzzles.
Where the game really shines is the use of the flashlight. This item has a standard limited battery a la Halo and Dead Space, but when you shine the flashlight on certain areas, the may glow a different color. If it glows orange, you can destroy it with your gun; green, you can destroy it with a grenade; purple can be destroyed or frozen with expanding foam grenades; blue, you can destroy it by running into it full-speed with the Friction Dampener boots; red takes a plain old missile. Because of this feature, I was able to figure out all of the puzzles except one-and that one takes jumping in an area the camera doesn't show after trying to destroy a hidden panel. Don't feel too bad about having to look that one up, especially since it was the only thing I had to.
The only complaint I have is that the game has a leveling system that is either mostly irrelevant or so subtle I didn't notice it-and the complaint is that it should have been more influential or eliminated entirely. You have 3 stats besides Health: Stamina, Precision, and Accuracy. I'm assuming these all tune your aiming in certain ways, though Stamina may affect how long you can run or hold your breath? Both negated by upgrades. Additionally, I completed the game in about 14 hours, and got to level 20. There is an achievement for level 50, and I have no idea how someone could get there. Higher difficulties purportedly grant experience bonuses, but unless that bonus is 250%, I don't see a way to get to 50 without cheesing areas with infinite spawns.
All-in-all, this game is definitely worth it if you have an Xbox and like Castlevania:SotN, Mega Man X, or Super Metroid. The soundtrack is excellent, the graphics are great, and the levels and puzzles are well-designed. The two big minuses are the completely generic story (but whatevs) and the lack of any teleporter-like contrivance. In such a large, open area, it was sometimes confusing getting from one side of the map to the other, and a teleporter or turbolift would have helped cleaning up that last few missile doors back by the entrance, etc.