I have only played Deus Ex, will play Skyrim soon. Anyway, I'd have to recommend both even if I have only played DE:HR. Deus Ex was an amazing game. It had a fantastic art style, a fantastic story, interesting characters, and great gameplay. From what I have heard and experienced in previous TES games, Skyrim is a truly massive game where you can do whatever. While Deus Ex will keep you playing till it ends, and then replays, Skyrim could keep you playing for hundreds of hours just doing random stuff.