Comparing Windows 98 to an NT-based general purpose OS like Vista is like comparing raisins to pineapples.... Rediculous.
For one thing, Windows 98-type OSes have no user mode/kernel boundary, are highly insecure and, well, are dead and gone for good. That species of OS is extinct and for good reason. There are so many significant differences in OS physiology that any meaningful
comparison is pointless.
Vista, with all of its apparent problems (some very real, some not so much) is the core Windows architecture of the forseeable future (core OS, kernel, HAL, base driver model, etc). Sure, Windows 7 will be an evolutionary release (I'd imagine - I know very
little about the offering, but that will change when the Windows team opens its doors to C9), but the
core architecture will most likely be very similar (and users don't care about core architecture anyway; and they shouldn't. The system should just work as expected.)