 If you liked
.hack//Sign
|
 ...then you might like
Fate/Zero
|
-Both are darker prequels of a big franchise.
-Both feature more mature characters.
-Both MC are cynical and have sad depressing childhood.
-Both focus more on building up characters; development, relations, background informations.
-Both characters seek a powerful mythical object; Key of the Twilight/Holy Grail.
-Both have less action but more well-made dialogues.
-Similar music (by Yuki Kajiura).