But I think this poll might be a little biased as there is not a Linux option...
Linux isn't the only other OS out there. Since he didn't name any non-Windows OS's, I think it's safe to assume he meant the best OS within the Windows scope of things. Not to mention that he titled the poll as "Which Windows
98SE was the best non-NT OS Windows made. From the NT bracket, Win-2000 was the better of the two (NT, 2k3). However, XP is pretty-much stand-alone from the rest, though it drew strongly from both 98SE and Win2000. So you could say that XP grabbed up the best of both worlds. Plus, out of the lot, 98SE and XP-Pro are the most stable Windows OS's available.