Platform: XBLA
Shadow Complex is the first serious and successful attempt at recreating the feeling of oldschool 2D exploration shooters inside a 3D canvas. It's plain to see they focused on recovering everything good from Metroidvanias, while removing the design flaws and problems arisen by hardware limitations. A new aiming system, leveling bonuses or an attempt at story-telling are some of the additions they made to the Metroid formula.
A bit of history
Since the introduction of the third dimension in videogames many attempts have been made to recreate the classics in the new environments. Most of the time, however, the results have been underwhelming. The fast action available in simple 2D worlds proved constantly too much for the more complex settings required for believable 3D scenarios, unless action was limited to only two axes (Robotron X, Einhander).
Until Zelda 64's lock on was introduced, few had managed to get things slightly right. And even after that, failure has been pretty common. Proof of this is the respected Castlevania series, which, after four 3D iterations, found commercial success only when Mercury Steam decided to break with the old game style completely.
The Metroid series did better, with the Prime saga achieving almost unanimous praise, thanks to its merge of FPS mechanics with a lock on system, plus subtle story-telling. It did, however, rely on completely different gameplay and narrative styles than its precursors.
There is, as can be seen, a common thread going on, which is not even considering a return to the 2D. That approach has been left for handheld consoles, with the Metroid and Castlevania series for Nintendo systems, or remakes of old classics and shoot'm ups, like Ghosts'n Goblins for the PSP.
Of course, there have been constant homages, with 3D games re-creating 2D gameplay in small sections. The one I remember most vividly is Nier, which achieved levels of meta-gaming off the charts. Castlevania: Lament of Innocence and Metroid: Other M also played with pseudo 2D, although not too succesfully.
Chair Entertainment played it safe, making Shadow Complex a 2D game inside a 3D world. Movement is limited to the x/y plane, while enemies are free to move all around. As a result, Jason, the main character, is allowed to shoot in any direction too. The game automatically chooses how deep you are aiming, and it seldom does wrong.
Metroidvania at heart
Shadow Complex is probably the highest profile metroidvania ever done: edge technology, a big studio devoted completely to it, an expensive marketing campaign and the push from Microsoft. The studio dedicated apparently several months redrawing levels in paper form, calculating possible advance routes, secrets placement and planning all kinds of distractions to get the player off the track.
Also, the Metroid games were studied to he deepest detail, until their inner workings were grokked by the team at large.
