DX:IW--The Definition of Gray Morality
Having said that, sometimes waiting is the best thing you can do. Allow me to explain: I suggest that anyone playing this game at this point in time should defintely do two things before beginning:
First, once you've installed the game, download and also install the Unified Texture Pack for Deus Ex: Invisible War (Google it). This amazingly comprehensive, free, fan-made texture pack (which I think was finalized sometime in 2007, four years after the release of DX:IW) pretty much redraws the game from the ground up (including all environments, characters, weapons), giving it a nice new shiny coat of paint, almost (but not quite) bringing it up to next-gen standards.
Second, in addition to installing the textue pack, I suggest if you are playing on a widescreen monitor (chances are highly likely you are in this day and age), that you also employ the Deus Ex Invisible War Widescreen Fix (again, Google it). DX:IW was released at a point in time when widescreen support was not very popular yet, and DX:IW does not natively support widescreen aspect ratios. However, this clever fix (courtesy of Widescreen Gaming Forum--a group that is also known as WSGF) will widen the game across your entire screen without stretching everything out of shape; this fix broadens the FOV (field of view), ostensibly widening the gameplaying area and giving you much more landscape to work with as you traverse the game. (One major earlier complaint about the game, especially in its Xbox iteration, is that many of the areas feel hemmed in and small--this fix helps to mediate that a little, but not entirely.) The widescreen fix requires a little bit of work and some hash calculating, as well as downloading one small program, but I'm no computer genius and the directions you'll find on the WSGF (or via Google) are straightforward, and it worked beautifully for me. With both the texture pack and the widescreen fix applied, you can play DX:IW at its best-looking ever--any earlier poor reviews based on graphical issues or limitations are hereby null and void. (BTW, if you are a gamepad hound like me, the game plays perfectly fine with one; I used the Xpadder program and a Wireless Receiver for Windows with my 360 controller.) Now onto the gameplay itself...
In agreement with many reviews here, the most immediate "big picture" comparison that comes to mind is Mass Effect. There's no denying that games like Mass Effect woud not exist if it weren't for the DX franchise. You've got a solid, complex sci-fi story that begins with a societal collapse; rather sharply drawn NPCs with distinct personalities and goals; complex organizations of people; politically charged, agonistic relationships among said organizations and the individuals within them; varied futuristic (but earth-based) locales from Cairo to Antartica; conflicting missions and allegiances you must choose among; firefights; dialogue trees; multiple narrative paths and endings, some minor rpg elements; biomodifications to enhance fighting or stealth abilities; upgrades to futuristic weapons. It's all there in first-person-shooter form--of course in a much earlier package which is just as ambitious but perhaps too limited technologically (for the time) to pull it off as successfully as a Mass Effect franchise.
Due primarily its age I guess, it was honestly a long haul for me to play, and I put the game down (shut it off, fell asleep with controller in hand, etc.) many times-stretches of lackluster action, an ornery graphical interface which was unnecessarily complex, stiff animations--regardless of the enhancements I already mentioned. (In between, I actually began and finished both "Metro 2033" [which lit me afire!] and also the 2009 "Aliens vs. Predator" games. But I persevered with DX:IW and completed it.)
Unlike Mass Effect, which rather steadily aims for the action crowd regardless of its complex narrative, DX:IW struck me as primarily a thinking-person's game instead of an action-oriented one (although it is, ultimately, a first-person shooter, without question). To that end, for a game with branching narratives and several different possible endings, this is the grayest of games (regarding moral choices you must make) that I've ever played--far surpassing Mass Effect in this realm. Given the world being played in (20 years after the Collapse, where everything--technology, the economy, society--went to hell), there are three or four opposing groups vying for power-each with a distinct plan they believe will help to revitalize society and keep it from sinking back into chaos. And they all make rather good arguments why their way is best (one group is more personal and anti-tech, another advocates spreading biotechnology throughout civilization to make everyone equal, another advocates spiritual as well as organizational/governmental changes, etc.). As we are all familiar with this game type, the choices you make will influence who your character becomes and what endings the game will show you. Of course, as one of your compatriots suggests, you can eliminate all factions and see what happens when there is a void to be filled.
Some reviews at the time of the game's initial release said that such a gray playing field helped to foment disinterest in the game. Are things more fun when there is clearly an "evil" path and a "virtuous" one? (Take Mass Effect as a case in point; Saren may as well be Darth Vader, black costume and all--there's no surprise who the evil dude is in this equation. On the contrary, DX:IW does not work like that at all.) Personally, I found the grayness very adult-like and refreshing (and much more real, in a way). For a game where I spent most of the time kicking myself to get through it for some reason, by the end, I was seriously contemplating (during time away from the game) which choices I should be making and what the outcome would be, since it is not very clear. That sort of thing does not happen often with me. I applaud the game for this.
Ultimately, I guess there is no best or right choice-just choices. I watched 3 of the 5 or so endings before getting bored replaying the last battles (which, if you want to see all the endings, you can do so by only replaying the final battles, each about 15 minutes long), and as it turned out, none of the choices were overtly wrong-but all of them very different, leading to different kinds of futures for our society post 2050.
So, the question remains: Will I play the long-awaited third part of the trilogy "Deus Ex: Human Revolution" (which has been in development for so long it has almost attained the lore of vaporware)? Eh, maybe? That is if nothing else is on the shelf at the time. I know--what a rousing endorsement. But that ambivalence--much like the characters you meet in DX:IW--is what I was left with overall after completing the game. I wonder if that was the developer's intent?