Hmm... at the time of DOS land, it didn't suck. It is kind of a milestone. Most machines that ran it launched it with an autoexec.bat and users only saw the fears black screen during the boot process.
Windows 3.1 did a number of OS type things, particularly himem managment. However, if you wish be complain because it had an msdos.sys "kernel" then you'd need to apply the same criteria to Win95, 98, ME, and pretty much anything that didn't get NT incorporated.
Windows 95 was a huge jump from 3.1. Almost as huge as 7 to 8. There was a paradigm shift with that little bar at the bottom. People complained. The final version of Windows 98 is essentially a fully patched Windows 95.
The final version of XP is probably Microsoft's climax. They really got most of the stuff they were trying to do with 95 done and got NT core out to the masses.
Vista is a cluster fuck. Windows 7 is essentially fixed Vista.
Windows 8... suffers from bipolar disorder. It doesn't know which context, Window 7 desktop-ish or tablet-ish, it wants to commit to, so fails to excel at either. Worse, it's inconsistent across hardware, the ARM version being limited.