[JAS84]

It's a shame the titles for the GN Show were ultimately butchered, because they were really good. Graham's talk shows were usually blessed with good theme tunes and title sequences.

Surely The Fresh Prince of Bel-Air must be up there with the longest title sequence?

The show didn't run for 20 years, so absolutely not. That's the benchmark to beat, as the first post mentions Homes Under The Hammer, which has lasted that long without ever changing it (and it's long overdue a change as it features now out-of-date banknote designs).