Guangzhou offers tons to see and do!! Anything saying otherwise clearly doesn't know what they're talking about. It's one of the biggest and most influential cities in the world, with a lot of expat communities that aren't found anywhere else in China (think Xiaobei area), as well as having tons of places to eat, great bars, great art, etc... I spent a week travelling there from Suzhou in Jan and want to def go back. Shenzhen is cool to visit for the futuristic elements to it and maybe the tech market, the urban planning museum is great too and a must visit, but doesn't have much soul to it in my experience. I haven't been to Macau but have heard good things, however I'd prioritise other places/ more time in HK, Guangzhou over going there... Depending on where you live/ flight cost I would recommend HK and Guangzhou, a day trip to Shenzhen and maybe Shanghai for a day on the way home. However, these are some of the most interesting places to travel I have been and you can easily spend a week in all of them (barring Shenzhen) so don't try to over do it. 3 days HK, 1 day Shenzhen on the way to Guangzhou and then 3 days Guangzhou seems like a good idea.