If I hear someone（esp. a very famous person) say something (e.g. a sentence) and I appreciate that sentence very much, what can I say?
"I like the sentence someone said" or "I love this sentence someone said" sounds awkward to me.
Both are fine, depending on context you might want to add "about"
I like the sentence someone said (about)...
I love this sentence someone said (about)...
If you use this usually you might quote the actual sentence you like.
I like the sentence President Kennedy said about going to the moon.
I love this sentence President Kennedy said: "Ask not what your country can do for you, ask what you can do for your country."