How good are they?
Deus Ex's success, in my opinion, is a huge fluke much like Fallout. When you actually look at the games in a non-biased viewpoint, you begin to notice they have incredible flaws (really buggy and ugly being one of the biggest although Deus Ex 2 was less unattractive) but when you actually play them, all the features add up to create a really immersive experience.
Deus Ex 1 was like a super fanboy homage to Blade Runner and System Shock with lots of conspiracy theories running wild. It was a fun game, pretty open ended, had a good plot, but was marred by bugs, an old graphics engine, incompatibilities with random cards, and all three endings could be achieved by making a decision in the last 5 minutes of gameplay which pretty much ruined the "your choices affect shit lol."
Deus Ex 2 was much different. They tried to streamline the game by removing the somewhat broken RPG stat rules from the first game (a blessing and a curse because a lot of people liked that factor), they streamlined the annoying damage system by making a single unified health bar, and they toned down the inventory by making ammo universal. Personally, I thought DE2 was miles above the first game. The voice acting was actually good (Tom Hall didn't voice 60% of the characters this time although he left the company to make Anachronox anyways), the storyline was 100x better (not to mention darker; the children academy side story actually disturbed me a little), there was a lot more emphasis on the characters themselves (there's three specific characters you develop a relationship with), and the game's combat system was dramatically improved so you didn't suck with every gun regardless of how high your skill was. The new biomods were also infinitely better and more useful. I barely bothered with mods in the first game.
I can't watch the trailer right now, but I'm excited. Project Snowblind was a decent action spinoff but if the game's action and exploration takes after BioShock (and with it's success, I know it will) and the storytelling follows the cinematic flair of Mass Effect, then I can see Deus Ex 3 being a fantastic game with a style of it's own. Deus Ex is
still one of my favorite game franchises and I've beaten both 1 and 2 once a year since they were released.