I think it was with the release of MC Hammer's single "U Can't Touch This" in June 1990.
[youtube=425,350]b9nptjUs9FM[/youtube]
I think the 90's were finally delivered a death blow by the Wachowski Brothers on November 5, 2003 with the release of the second part of a one-two punch of Matrix Reloaded/Revolutions, crushing not only fanboy dreams for the last great (potential) movie franchise of the 90's, along with the Sci-Fi/Hacker/Black Leather Fetish/Cyber Punk/Neo-Noir fad that brought us such films as Barb Wire, Johnny Mnemonic, Dark City, Hackers, The Net, Equilibrium, Judge Dredd and more, but it also killed Keanu Reeve's career. The 90's would never recover from that.
Discuss.