I would go for DE
Some stupid motivational

Honestly, it depends on what you are looking for. I love them both, but they are really different styles of games.
The best way to explain this is to use movies for example. I think everyone will admit that The Godfather is a rather good film, at least from a directorial and script point of view. And I think that many of us will admit we enjoyed the hell out of watching Commando. I doubt anyone could, with a straight face, say that Commando was a better movie. But, for a lot of people, it is a more enjoyable one.
Same thing with Deus Ex (although DE is at least a really fun game as well :p). There are few games that are better. But it might not be what you are looking for at this very moment.

All the FEAR expansions were crap. So much that their entire story was retconned by Monolith.

Deus ex. It's just one of those games that you need to play if you haven't.

Deux Ex and you get to play The Nameless Mod as well, which is really a big fat bonus.

Thanks everybody for great answers, bought Deus Ex and LOVE IT...only one more question : What is the state with the High Def mods? Are they finished or at least in state that game will be playable? Should I play the game with them or play it with original textures?

I'm in this same boat, actually. I played DE back when it first came out but have decided to give it another run-through as a result of the announcement of the new title. But I caught wind of a lot of high-def mods that seemed largely unfinished. Has anyone used them?

This.