In entertainment, are you all referring to just the movies played on board or to all entertainments including newspaper, magazine, music, .......?
IMHO, the newspaper and magazine selection are much better on CX than SQ. This is partially due to the fact that I am from HK and am used to the local newspaper and magazines. But I did notice on several trans-pacific SQ flights that the selection of magazines was almost non-existent. And whatever is available aren't that good anyway.
As for the music and movies, the selection on both are fine and SQ used to be miles better since they were the only one with VOD. But CX has caught up in this respect and on my most recent trans-pacific, they have VOD also. SQ does have a better/bigger screen though.