Windows 2000 was definitely an all-around improvement over NT4, but it wasn't marketed as a successor to 98. That was Windows ME, which in hindsight was a bad idea. Microsoft should have abandoned the 9x line after 98 SE and put all their resources into making the NT line suitable as a replacement for the entire customer base. But for some reason they decided they couldn't pull that off in time for Windows 2000, and postponed the unification of the product lines until XP.