Well, I have recently made the most miserable purchase I will ever make in my entire life: I bought Deus Ex 2. I paid fifty dollars for what must be the biggest letdown ever.
Where to begin? Well, first of all, I'll go with the thing most Deus Esx fans will notice first: the lack of a skill point system, and all I can ask is... why? Why take out the single most important feature that made the first game so great?
Then of course there are the graphics. They're pretty, of course, but they're pretty in the wrong way. Damn near everything in DX2 is either reflective, glossy, or chrome. In the original, society was on the verge of collapse, and everything was rusted, scarred, and just plain dirty. It really got the feel of the game across. The graphics in the sequel make you feel like you're playing through an enormous Mitsubishi commercial.
The combat has been dumbed down, as well. It used to be that you could have your right arm shot to hell, losing a lot of accuracy, or you could get both of your legs turned into chowder, forcing you to crawl around. And of course, headshots were lethal.
Not anymore.
In DX2, you can spend half a clip blasting someone's head apart, and get the same amount of damage as you would by shooting them in their pinky toe.
Music? Don't get me started. It's okay, but it doesn't convey the mood like the tunes in the original did.
The conspiracies have gone out of whack, too. In Deus Ex, ALL of the conspiracies are based on actual conspiracy theories. In DX2, they're starting to just make stuff up.
Ion Storm has single handedly taken away EVERY SINGLE ELEMENT that made the original so incredible. I don't know why. Maybe it's a company full of sadists, because they sure have raped me, charging $50 for the world's shittiest sequel.
EDIT: I almost forgot: "unified ammo." All guns use the SAME KIND OF AMMUNITION. I don't even have to explain how fucking stupid THAT is.