The pioneer- Metal Gear Solid | 1998 | PS1
Hiding under a cardboard box. That was Hideo Kojima's answer to the prevailing tide of titles that focused on blasting seven shades of excrement out of anything that had the misfortune of moving. But this pedestrian activity was little short of revolutionary. MGS brought us strategy elements both previously untested in the US and in 3D, favoring concealment rather than confrontation at all times, however you could manage it. Using cigs to reveal laser trip wires, porn to distract guards, even tapping the walls to lure a guard down a dead end and strangle him out of sight. It was all hugely inventive - and liberating - stuff. Piss and moan all you want about its philosophical bent, but this game carved out an entire genre for itself.
Raising the bar- Splinter Cell: Chaos Theory | 2005 | Xbox/PS2/PC/GC
The pinnacle of the Splinter Cell series, even in light of the recent release of Double Agent. Where MGS introduced a mantra of general avoidance, Chaos Theory challenged you to be invisible, offering up a complete reworking of the basic stealth concept. Gone was the humor, the overblown showdowns and freak show characters, replaced with an altogether more sober and realistic affair. Increased emphasis on using light and sound to your advantage, and severe penalties for drawing attention to yourself made play more plodding and thoughtful, but in turn we got a whole host of new toys to play with, from optical cable to airfoils. Then it heaped on adelightful online co-op and spies vs. mercs multiplayer. You just can’t beat that.