Deus Ex: Human Revolution is a prequel to the original game that took years to develop, cost millions of dollars and drastically re-imagined the look of the universe. That was cool with many people, but if you prefer the original, you should check out this fan-made project.
Billed as another Deus Ex prequel, 2027 is a total fan conversion of the original game, using the same engine and tools to build an all-new story. It even improves a few things, with added graphical tricks, bug fixes, and new weapons, plus it also drops a few new unit types in as well.
While it was made by Russians (like so much other amazing PC mod work), there's now an English version available. You can get it at the link below.