I'm not a big fan of the horror genre but the Bioshock series won me over with sci-fi elements and interesting story. I enjoy the expanded universe content and can't wait for the 4th installment even though it's going to be a good while before Irrational Games works on another one. Co-op was missing in the games but kept the spookiness of singleplayer horror. I'm glad they included 1999 mode. What did you like or hate about the series?