Some of the cases listed are clearly trying to imitate the G5 tower, but I thought many of them looked nothing like the G5 tower with the exception of the prominent handles on the top and bottom. However, that is like saying all humans look the same because we all have ears.
I like PCs and Macs. I wouldn't want my PC to look like a Mac and I wouldn't want my Mac to look like a PC. I just have a boring gray mid-tower right now, but when I build my next machine I'm getting the case windows, internal lighting, the whole nine yards. Yes, it is kind of gaudy but when you spend time picking out each and every component you want in your PC and you're putting quality stuff in there and laying it out well you want to show it off and geek out. Would it look nice out in the living area? Hell no! That's why my PC is in the bedroom with the CRT and large, clunky monitors and the Mac mini with my LCD and wireless keyboard/mouse is out in the living area.
Different uses, different styles... I like 'em both for different reasons. Of course the Mac wins out for overall beauty, but the flashy/gaudy pimp'ed out PCs have their appeal for me too. It might not be high art, but I think it's cool.