For me personally, Deus Ex is my favorite greatest game of all time, despite all its flaws and jankyness, and I'm not the only one who thinks so. There's a reason why “Whenever someone mentions Deus Ex, someone reinstalls it.” meme exists.

I was genuinely surprised by how profound the story of Deus Ex is and how relevant it remains today. Like everything related to consolidation, mass surveillance, and so on, it's even a little scary. And this is a game released before 9/11, about silly conspiracy theories. Many people give credit to Hideo Kojima for predicting stuff in Metal Gear Solid 2: Sons of Liberty, but I believe Warren Spector deserves as much praise for his work on Deus Ex as Kojima has now.

Dialogues are good*

Despite the fact that the voice acting is generally mediocre at best (*and in some places either great or completely terrible), the dialogues are more believable and realistic than Hollywood-esque dialogues in AAA games, thanks to the way they are written. They have a certain charm (much like the dialogue in The Elder Scrolls IV: Oblivion) and in some cases even memeable (especially JC's expressionless one-liners).

Soundtrack is amazing.

I absolutely love the soundtrack composed by Alexander Brandon, Michiel van den Bos, Dan Gardopee, and Reeves Gabrels. It fits the atmosphere of the game very well, is unique for each level, and has separate versions for combat and dialogue (funnily enough, the composers didn't actually play the game, but simply wrote the music that just fitted the theme judging by a brief description of the level). I also like that the soundtrack has a main theme motif in some tracks, which often makes it sound a little more epic. A bit unrelated, but I'm a huge sucker for Module Tracker music, and Deus Ex soundtrack is one, composed in Impulse Tracker.

Rite of passage.

There's one thing in Deus Ex that makes the "casual gamers" quit the game (if they could tolerate the graphics in the first place) and its the gameplay. I had to get used to the gameplay myself, hell, when I first tried playing Deus Ex, I just quit. Why? Imagine you've just completed the UNATCO Academy course (Training Mission), thinking, “That was a little weird, but not too bad,” you select the New Game, choose your difficulty level, and see a very confusing character creation screen. Okay, RPGs like Fallout or Star Wars: Knights of the Old Republic did that too. You either ignore it or put points into skills that you think will be useful and watch an equally confusing cutscene that will only make sense once you've completed the game and put all the pieces together.

After watching the intro, you find yourself on Liberty Island and (once again) get confused, this time because the game asks you to pick your weapon of choice. You choose one and leave the docks, only to get shot in the face (or, if you're lucky enough to sneak past or kill your enemies, somewhere else). This repeats until you say “Enough” and quit the game. The Liberty Island mission is infamous for being some kind of unspoken and unforgiving rite of passage, but once you get past it, you'll get used to the game and start enjoying it. And there's one more thing that most players probably won't learn until they play the game for a second time. You can play Deus Ex however you want. Really.

Wanna go gunblazing?

Put on ballistic vests, upgrade your guns, get the Regeneration and Ballistic Protection augs, upgrade your Rifles and Pistols skills, and you're all set. Or you can use non-lethal apporach. Yes, you can suck at stealth, but spray the conspirators like cockroaches (with pepper spray or a flame extinguisher) and beat them with a baton or taze them with a prod.

Wanna sneak like a kid running messages?

Right from the get go. You can also use tools such as a baton, mini crossbow, thermal camo, Silent Run and Cloak augs, they'll be useful. Just don't forget that you must hit your enemies in the lower back for maximum damage.

Wanna ignore everyone and be as chaotic as possible, while not harming anyone?

Sneak past enemies or run through them, rob people, and throw objects to distract enemies (they react to the sound of darts hitting the wall/ground, thrown bottles, flares, food, and other objects landing).

Its up to you.

I've done a bunch of different playthroughs, and each playthrough has been interesting and sometimes challenging, and I've enjoyed it (and still do). And that's one of my favorite things about Deus Ex: the game doesn't restrict you on how you want to play. Go wild. The game won't throw you in the game over state if you failed sneaking or have no "solution" to solve a problem, because there are different ways to solve the same problem.