Deus Ex is an amazing game.
The game's story doesn't seem like anything special at first. You're a police agent sent to fight the terrorists and find a cure for Gray Death, a plague virus that's menacing the whole world. However, there is a lot more come to the story. Before you know it, you'll be wrapped up in a vast conspiracy and will be sent all over the globe to neutralize the threat that keeps growing bigger and bigger. The thing with Deus Ex's story is that it actually isn't anything special. It's pretty predictable and doesn't contain a lot of major plot twists, but it's very intriguing and thus, makes you want to play the game for aimlessly long just because you want to know what's going to happen next. And that's the sign of a great storyline.
Deus Ex is one of the few games with an unbeatable gameplay. No one other game has, and never will, succeed in combining FPS, RPG and stealth genres as amazingly. Stealth is the definite keyword of the game. You will have to move slowly and quietly, make sure you are not seen, keep your ears open to hear if the enemy is near and knock your enemies out silently. Going through the game with all guns blazing is possible, but very hard much thanks to your character's vulnerability and a bit clumsy fighting mechanics. The fighting in the game is quite clumsy indeed because your enemies have a tendency to shift from left to right around you and keep moving like hell. Maneuvering your character is a bit hard and clumsy, too. But that doesn't really matter to me because most of the game can be gone through using stealth and trying to avoid combat as much as possible. There are many ways you can avoid and bypass your enemies, and that adds a whole lot of replay value to the game.
Upgrading your character is also quite flexible. You can either choose your character to be, for example, an expert hacker and lockpicker or a heavy weapons and demolitions expert. However, there are only the few augmentations and skills you're going to need often, and the rest are pretty much useless. Other role-playing elements include talking with other people and that way, learning some new details about different people or some hints to achieve your goal and complete your objectives. This is a pretty good quality too. You are not instantly told where exactly something or someone is. You need to read e-mails and computer terminals or interrogate different people to get some useful advice or details about your mission.
The level design of the game is also great. There are a lot of areas and places to discover and explore, and on every single playthrough you are guaranteed to find something new. In Deus Ex, it is always good to explore every single available area because you never know whether you're going to find a weapon modification or some useful tools to bypass the security with. This adds the game a lot of replay value, too.
One of the game's highlights is the amazing, cyberpunk-themed atmosphere. The whole game takes place during nighttime while you have to explore the dimly lit streets of New York as the mind-blowing soundtrack is playing in the background. The soundtrack is indeed one of the best video game soundtracks ever, greatly combining electronic techno music with a pop-styled catchiness.
Having to mention some negative sides of the game, the first ones that come to my mind are the clumsy combat mechanics as I already mentioned earlier and the unbalanced AI. While the AI can sometimes be pretty good, becoming suspicious if you make noise or if they catch a glimpse of you, they usually ignore bodies and don't even start a search party if they think you're around. Another funny example would be as I in one mission fired a grenade launcher at a couple of barrels, creating a massive explosion and killing all the guards in that room. Another guard comes to check the area having heard the noise and after a while, calmly leaves as if nothing had happened. "Nope, just my nerves". This is the only "major" flaw I can come up with in the game, but other than that there are none.
Shortly put, Deus Ex is one of the greatest games of all time. With an amazing combination of different genres, comprehensive gameplay, terrific atmosphere and a storyline that definitely sucks you in, you've got yourself one extraordinary video game adventure that you'll want experience again and again for years to come.