1. Deus Ex (PC, also on PS2)
So, finally we reach number 1. This is quite simply the greatest game ever created! So many different play-styles, so many different decision trees, and a fantastic story to boot. If you like FPS or you like RPGs (even better if you like both), this game has to be played. The tech may be old, but the story and the gameplay are timeless.
Set in a cyber punk world (set in the not too distant future) where a wide array of hidden political groups, terrorist factions, freedom fighters and advanced computer AI are all vying for for their ideological future. You play JC Denton, a new nano-augmented agent for anti-terrorist organisation UNATCO. The first level shoves you in the deep end and immediately sets the tone for the rest of the game. You enter the docks to find terrorists have attacked the base to steal the months supply of a vaccine for a global plague. You're tasked with finding the terrorist leader (alive). Immediately, you're brother (a fellow agent) gives you the option of which weapon you want to carry: crossbow, sniper rifle or RPG.
You then have multiple options; Do you use stealth and sneak around? Do you go to the other side of the island and meet with the contact for the key to the front door? Do you pick the lock? Do you find a back way in? Do you hack the security systems and disable the cameras? Do you make for the ammo caches first? Do you go in guns blazing or silently take them down? Do you kill your enemies or just stun them? Do you avoid them alltogether? Do you bother with the secondary objective and save the captured agent or leave him? If you do rescue him do you give him a gun? When you reach your final objective do you follow orders or outright kill him?
All those decisions are on the first level and can have an immediate effect on the way other characters interact with you. In the future, the choices you make have serious repercussions on the characters around you including whether they live or die. The repercussions aren't always clear-cut either. Whether your pilot Jock lives at the end of the game is based solely on your curiosity rather than a clear positive/negative decision tree seen in most RPGs. All these decision trees and the detail in the world (you can drink and eat food, read newspapers, hack computers to read e-mails, get drunk/high etc.) make this game deeply immersive.
The games is ridiculously immersive to the point of embarrassment for me. I actually mistook the beeping of a stopwatch (in real life) for the sound the explosives make when they're about to go off and dived into the opposite room. Luckily, no-one saw, but yeah...
I haven't even talked about the story yet. The storyline is one of the best in video games history. A deep and involving plot that combines political intrigue, conspiracy and advanced science into one amazing package. What's so extraordinary is that it manages to retain an excellent storyline whilst still giving the player such huge freedom and choice. Only a select few games have ever acheived this, and I can't think of one that had as much choice as that offered in Deus Ex.
Add to all this the variety of weapons that included a measly batton/knife, grenades (EMP, gas, explosive), assault rifles, shotguns, RPGs, sniper rifles and massive energy weapons, and the variety of nano augmentations (Enhancements) that included invisibility to either bots or organics, healing, super speed and jumping, spy bots, balistic protection and visual enhancements, and you get an amazing package.
So the game was perfect in single player, many will complain the multiplayer wasn't that good. I entered the multiplayer with this in mind but have to say, I found it thoroughly enjoyable. The sheer variety of weapons and nano-augmentations kept it fresh and different and was actually a lot of fun.
Bascially, this game is increddible, and if you haven't played it, you owe it to yourself to give this a go. Oh and it also predicts the future as it predicted 9/11 a year before it happened! Play this game for a view into our future... woooooo!