A Sci Fi publicist has answered my question re ''Stargate'' and ''Doctor Who.'' I may be doing more research on this, but here's the answer for the record:
Guinness awarded the title of longest-running sci-fi series in tv history to Stargate, which took the title away from X-Files (at the 203rd episode, technically). Both shows overshadow Doctor Who in that they had consecutive episodes. Doctor Who while it ran several hundred episodes, had long gaps of not being in production, far longer than a regular hiatus. The show was revived several times and I'm told one of the gaps between production was over ten years.