I'm interested in Human Revolution, should I play the old games?

Games? There is only one Deus Ex game currently out, and yes, play it.

i tried the first one a month ago and god DAMN did it feel lame

  I think the first was absolutely amazing and just finished it again a year ago. The shooting may be way out of date with the way it feels, but the story and world is just so friggin' cool. Oddly enough, Vampire Bloodlines feels very similar to the original Deus Ex if you've ever played that. However, I don't think I could speak for the gamers that maybe never grew up or played those types of games. It could be a little to odd and you may feel like your stumbling through the game instead of actually becoming any good at it.
 
I could'nt finish the second one becasue it ran so damn terrible. Apprently there is a patch for the second one that fix's the frame rate and such, but I never tried it. 
Isn't Deus Ex, like 2.50$ on steam or something? Definitely worth that, even if it is just to say you have played it.

The first Deus Ex game still holds up to this day. Brilliant piece of work. Invisible War... well, I didn't think it was that great when it was released so I assume it feels dated now.

First Deus Ex is a great game. The second one is a OK as a game but you can't compare it to the first DE, It's way too streamlined for that.

It's a prequel, so you really don't need to.

Invisible War might be worth a try... The original hasn't aged well.

I think the first one does, sure (haven't played the second). Of course it will feel a little old, but you'll get used to the mechanics in the opening mission.

" @Metal_Mills:  There are two. Deus Ex and Deus Ex Invisible war, (regardless if you want to count that one or not.) "

It absolutely holds up. Don't let the dated feel or the graphics hold you back, it's an amazing game.

I played the first one two days ago for the first time.
 
Gah that game felt broken.

I played it last year for the first time and honestly, it was nothing special in my eyes-- it just felt dated. I can see how it was revolutionary and I did however enjoy the Hong Kong level. It was VERY well designed. I will probably pick up the sequel and no I never played Invisible War. It was a good story too even it it reminded me of Metal Gear Solid too much even despite the ending cutscenes being around 30 seconds the impact was great.

 Don't forget that there are graphics mods out there. It holds up just fine but I guess if you didn't play games 10 years ago it feels too dated or something?
  
If you have the steam version.. links to the mods too if you just need them.
http://forums.steampowered.com/forums/showthread.php?t=1235278

"Oddly enough, Vampire Bloodlines feels very similar to the original Deus Ex if you've ever played that."

You can try but don't push yourself. If you don't like it after a couple hours then don't bother. That being said if you are willing to push through it is one of the best RPG's of all time. Even the "prequel" had some ideas that were revolutionary.

Buy the first one off Steam, install some graphics mods, make sure you have the right renderer selected and resolution cranked up. Start a new game, put some points into pistols right away if you're interested in actually being able to shoot anything (otherwise stealth is pretty viable) and away you go. Awesome game.

There's also a ps2 version of DX1 if you're into consoles.

I played the first Deus Ex about a year ago for the first time and got about fifteen minutes in before shutting it off and thinking "This is terrible." Then, I finally decided to try it again a couple of months ago. After I finished the first mission and actually got involved in the story... wow. That game is amazing. It goes on my Top Ten list. 
 
 
So if you're willing to put up with some lame graphics and kind of dated shooting to get involved in the plot, I think you'll find that it has not only aged well in that regard, but it's still better than most recent shooters.

The shooting mechanics were not perfect, point based skill system on weapons felt awkward then and they still feel awkward now (Alpha Protocol aiming feels almost like the original deus ex and it got hammered alot by critics).  But in terms of story, character progression,  various ways to do a mission, and decisions you make was original for it's time and that part of the game still holds up and is very enjoyable.
 
As for invisible War, it was actually a good game.   It streamlined alot of stuff,  probably a bit too much from the first game.   The story wasn't as great and the level design was a bit compact compared to the first one.  The biomod system was a bit too simple as well.   The shooting was actually improved dramatically and i felt the ammo system was appropriate, and stealthing was pretty fun.

i just beat the ps2 verson The conspiracy  and i have to say god its one of the greatest games i have ever played the grapics dont but hell who cares about that its still a Fantasitc game if you got time to play it play it you will not be sorry.

The first Deus Ex was a great game...back then. If you play it right now, you might be turn off by its slightly outdated Unreal graphics and gameplay. But at least it has a decent plot so if you're into storyline, you might enjoy it. After all, Deus Ex won numerous Game of The Year awards so it can go wrong. I'd say give it a try. 
 
@Jimbo said:

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I think even the gameplay is deeper than many other games today. Give it a shot, you might not like it as much as I did, but it's worth a try.
 
I played it 2 years ago for the first time BTW, and I still loved it.

There are some mods out there that help with the aging process. 
Before.