I hear this a lot and it's a poor model that shows an ignorance of the products or perhaps a lack of historical context.
A more accurate model:
Consumer Line
Win 3.x (kind of crappy, but whatever a first attempt)
Win 95 (Much better)
Win 98 and 98SE (incremental improvement)
Win Me (a crappy OS pushed out the door after OEMS balked at the idea of selling an OS that required the 3 finger salute to log in -- We were supposed to see Win 2k Pro or some variant as the unification of the consumer and professional code)
Win XP The realization of the aforementioned consumer/professional OS unification. Most people loved it, I thought it was kind of a step back from Win 2k, but it (eventually) added wireless network support and a couple of other need to have features.
Professional Line
NT 3.x Server and Workstation - fine for what it was.
NT 4 Server and Workstation - Pretty solid for small/mid sized businesses maybe not quite robust enough for enterprise application, lacked some features that you'd really want to see in a consumer desktop.
Win 2k Server and Professional - MS builds a server for the enterprise, it's not bad. Professional works great as a consumer desktop OS, but is never marketed as such. Big improvement over NT 4 for a business client OS.
Win XP See above.
At this point, MS has moved to the NT code base for both the business and consumer markets and dropped the old DOS/Win95 product line entirely. They now split the client and server OS's into different product lines.
Client
Win Vista - Ok, this one blows. There are some areas of improvement, but some obvious botches...
Win 7 Seems to be generally well regarded. The best client OS MS has ever made in my opinion, but then I always disliked XP.
Win 8 - Seems to be a looser. I've not used it enough to have a real opinion, but the consensus seems to be that it's another Vista...
Server
Win 2003 - Solid improvement over Win 2k.
Win 2008 and 2008 R2 Another solid improvement (or 2 in a row depending on whether you count R2 as a separate release).
Win 2012 I've not used it much yet. Seems to suck down a lot more resources than '08, but computers are a lot more powerful. Time will tell.
So, to sum up...Win 3.x - consumer line, bad. Win ME - consumer line, living abortion, bad. Win Vista, client line, bad. Win 8, client line, bad? At most the pattern can be said to work for Vista,7,8 looking at only the client line of OS's.
Slashdot Mirror
A more accurate model:
Consumer Line
Professional Line
At this point, MS has moved to the NT code base for both the business and consumer markets and dropped the old DOS/Win95 product line entirely. They now split the client and server OS's into different product lines.
Client
Server
So, to sum up...Win 3.x - consumer line, bad. Win ME - consumer line, living abortion, bad. Win Vista, client line, bad. Win 8, client line, bad? At most the pattern can be said to work for Vista,7,8 looking at only the client line of OS's.