Gerry Anderson will probably never be recognized as an the icon of Sci-Fi TV that he should be. His most remembered series, Space: 1999, tends to be derided in SFF fanboy circles who focus more on its failures (mostly involving the second season in which Anderson had lesser involvement in) than it's successes. And UFO is a outstanding SF series for its time that is not as well remembered as it should be. Also to his credit is the remarkable film "Journey to the Far Side of the Sun" (aka Doppleganger).
The massive amount of coverage and tributes all over the press and media show that he clearly is recognized as a major figure - in Britain at least. And he's probably the only tv producer to have his own fan club. As others have said, Thunderbirds is and always will be his most successful and best remembered series. The fact that 45 years later, the vehicles and characters such as Brains and Lady Penelope are still recognized as cultural icons, such that they can be used in tv commercials and the like without any need of explanation or introduction, must demonstrate that.
What's perhaps not best remembered is what Gerry Anderson actually did. (My girlfriend demonstrated this to me the other day when she commented that she thought he was a puppet maker.) And his MBE was awarded for "services to animation" which demonstrates that the honours committee only thought Dick Spanner, Lavender Castle and New Captain Scarlet were worthy of note
- or that they too had no idea what he actually was famous for.