My favorite animal is the monkey.  Do you like monkeys? 
I love monkeys! and they are generally considered very intelligent, specially Old World monkeys.
What distinguishes Old World monkeys from New World ones? 
Old World monkeys are from Africa and Asia and New World monkeys are from South and Central America.
Why are old world monkeys more intelligent than new world? 
I don't know that or even if that is true is what is believed. Of course there are also the Hominoid apes (e.g gorillas and chimpanzees) that lack a tal.
Ah yes the apes though are not as fun as monkeys in my opinion.  
True but I like them too and some of them seem pretty intelligent, even speaking with signs. They are a branch of Old Worls monkeys and also come from Africa and Asia.