I just arrived in ICN today at around 1 PM and I was off the plane, through immigration, got my bags and went through customs in less than 30 mins. I fly in and out of ICN a lot and find this is was a fairly typical time, though it can of course vary on peak days and due to the factors A_Lee mentioned. Flying out of ICN I am typically in the lounge within 20 mins or so, rarely ever longer. I really don't find these waiting times to be in any way bad. I typically get through immigration in less time in FRA (but then I am an EU citizen), but security is extremely hit and miss. You can basically forget about the US (even as a US citizen) and SIN is the only Asian example I can think of that is consistently quicker than ICN. HKG is fine, but my experience has varied more.
All this to say that I really don't get why anyone is complaining about the speed in ICN. Now whether that makes it the best airport in the world depends on a whole host of matters and how much weight you give them. On most measures I would say it is at least way up there by global standards, though there certainly are other contenders.