DVD, then. Although that's sort of cheating since it's such a natural evolution from CDs -- it was clearly better than VHS and it didn't take any convincing for people to adopt them.
(you'll probably point to DIVX but that was an experiment with a terrible business model, not a technological failure)
> However, like many ideas far ahead of their time, the CD-ROM found few interested investors at first.
And then in 1975:
> Philips Electronics representatives visited Russell’s Battelle lab in the summer of 1975, and they discounted the entire premise of his work.
[1] http://www.computer-timeline.com/timeline/james-russel-compa...