Battlestar Galactica, Knight Rider, James Bond, and to a degree the new Trek film have all had their continuity altered or changed, or given a fresh POV. However Doctor Who, like Star Trek TNG before it, is a continuation of the original series, although like with TNG it's clear somethings have changed since then (TNG-the peace with the Klingons, for instance, and new technology such as the holodeck, while WHO of course had the time war). It's obvious it's still in the same continuity though-Sarah Jane, for instance, and various other elements such as returning villains plus the ocassional continuity nod to the classic fans ("Dr.Jaime McCrimmon" for example, Captain Jack being a "Time Agent" and various other references). The only element I can think that's really changed is WHO's vision of the future, but even that was inconsistent in the classic series (How many Atlantises, Loch Ness Monsters, and end-of-the world events are there?) The novel writers attempted to make a coherent timeline for WHO, but even that was frought with problems.
However, what if WHO had decided to start from scratch? This was apparentally a concept they were thinking about for the TV movie over a decade ago, with some kind of mess about Borusa (The Doctor's time lord teacher from various time lordcentric serials in the classic series) being the Doctor's father and companion or some weird stuff like that, but ultiametly that too was dropped in favor of continuity with the classic series by including Sylvestor McCoy.
However, what if WHO had decided to start from scratch? This was apparentally a concept they were thinking about for the TV movie over a decade ago, with some kind of mess about Borusa (The Doctor's time lord teacher from various time lordcentric serials in the classic series) being the Doctor's father and companion or some weird stuff like that, but ultiametly that too was dropped in favor of continuity with the classic series by including Sylvestor McCoy.