You forgot Windows 3.1.
oD&D = DOS, a basic, very workable framework on which the system would be built for many years, without the familiar user interface
AD&D = Windows 3.1, an inspired (by Mac

) attempt at a substantially improved user interface, widely adopted, extremely buggy
AD&D 2e = Windows 95, clarified, easier to use, and just as buggy
AD&D 2.5 (player's option) = Windows 98, but the analogy doesn't work because 98 was a much more stable system than 95
D&D 3e = Windows NT, what serious users had been using for years (in the form of other, more refined RPGs) but which wasn't previously integrated with the home system; more stable; not completely compatible with other versions
D&D 3.5 = Windows ME, upgrading and patching NT into the main system; compatibility with prior versions of the home system was starting to fail
Star Wars Saga = Windows XP, substantially more attractive, stable and easy to use, quite different in appearance.
We can only hope 4e works better than Vista.