This thread makes me feel glad i transitioned to PCs after my N64. PCs were always less susceptible to this problem and i was always good at helping it.
For the worst loading i have experienced i will have to go back to the home computers era. Mainly the 8-bit computers that used cassette tapes. I didn't own one, i was very young for that era, but a friend of mine did still play with his Spectrum in the early 90's. The loading times were so long, they became some kind of a ritual, to the point where old users remember those loading screens with nostalgia and claim they were part of the experience.