Grammar Nazi!

A student recently posed a question to me:
Why do we say:
"This news is nonsense to me."
and
"This game is difficult for me."?
I can't find anything on it in my grammar textbook, and the best I can come up with is that the second one is describing an activity, and the verb "to play" is implied at the end. Whereas the first one is describing a thing, and the comparison "looks like" is implied somewhere. Is there rules on this stuff or what?
Why do we say:
"This news is nonsense to me."
and
"This game is difficult for me."?
I can't find anything on it in my grammar textbook, and the best I can come up with is that the second one is describing an activity, and the verb "to play" is implied at the end. Whereas the first one is describing a thing, and the comparison "looks like" is implied somewhere. Is there rules on this stuff or what?