The long, burdening, inherent length of the phrase truly shows the user's approval of what/who he/she is directing the phrase at because it rejects the laziness and ease of staccato approval words such as "cool", or, "favorite."
Sami: Look at my sloth hands! Aren't they adorable?
Abbey: You guys are just the cookies and cream!
Abbey: I'm so cool.
Jake: The cookiest and creamiest, if I may say so myself.
Jake: What's your favorite ice cream?
Joe: Cookies and cream.
Jake: That's cookies and cream!
Joe: I know, that's what I said; cookies and cream.
Jake: Cookies and cream!
Joe: Stop it.
Jake: ....cookies and cream?
Joe: You're fired.