Dat, minidisc and betamax were great products, minidisc and dat are still widely used
betamax was a better format than vhs and the beta format is still widely in use
all three of those products failed in the consumer market because of who they were manufactured by not because of what they were but were successful in the professional market.
The same goes for HDDVD, better than blu-ray but not manufactured by a company that owns the rights to a frightening amount of the entertainment industry's intellectual property.
new coke is the best example i reckon, along with anything ever made by amstrad ever and pretty much anything made by rover after 1985