CG is without a doubt my favorite. Everything runs smooth; the storyline, the characters and the action are all mixed up perfectly. I found Mirai Nikki and Guilty Crown pretty similar, though I disliked the protagonist in MN, a stupid whining kid who keeps crying and complaining without doing actually grozit. Other than that, everything was pretty entertaining.
I am searching for something alike those three, I like the psychological war CG has and also the complexity of the characters: C.C. from Code Geass for being so misterious and yet revealing her so easily, Lelouch for his incredible deductive ability and Yuno from Mirai Nikki for being able to shift from the overly attached girl to the killing maniac and back, something which made the anime far more interesting that I had firstly thought.
I personally dislike romance being the main plot in an anime (had the bad luck to watch Infinite Stratos and Sankarea). Code Geass mixes that really awesome (refering to the Shirley - Lelouch relationship; it's perfectly balanced and integrated into the storyline).
I also liked Elfen Lied and Death Note, both great anime (story-wise). Highschool of the Dead had much potential from the first episode, but ended up pretty much as a disappointment.
I would prefer to see suggestions with a small description of the anime, as well as the similarities to the ones stated above. I would also enjoy discussions about these anime, so feel free to add me on skype (illidan_hunterr) and maybe here too.
All hail Lelouch,