The difference is that a maze gets visitors something to do, big builds are usually only there for eye candy. You look at it, and that's it.
I'm not saying it's no longer impressive to pull off a huge build, but I am saying that because everyone is doing it...
Take EMC... Most players have shops, and most players who want to go bigger have malls. Some of those look very impressive (HSP ("Horse Shoe Plaza") on SMP2 for example) but because there are plenty of malls the size is no longer as impressive as it used to be. It's still impressive but in the end it's a build like so many others.
Hop onto a server and you get an impressive spawn.. hop onto another and there's yet another spawn. But looks alone aren't enough anymore IMO.