So, let me be the one to come out and say this:
I've been in several interviews, both at startups and on more-established teams, where a record of no-traction startup failures was a real neg. It can have the appearance of someone who doesn't want to buckle down and work.
There is no reason --- none at all --- that you should put disfavorable information on your resume. Pick a couple (2) of the most interesting-looking attempts and showcase them. Leave everything else out.
Obviously, subcontracting, consulting, temp, and meaningful volunteer and open-source work should get written up. If you worked for name-brand clients who you're allowed to mention, and you were there for more than a couple months, list them as if they were jobs, with a subhed like "on behalf of XYZ Consulting, Inc.".
If you did most of your self-employed work under a single umbrella company name (and, everyone else, here's a good reason why you should), list that company for the largest possible time span. Freelance work counts! Having helped run a consultancy for 4 years now, I'd look more favorably on someone who managed to keep a freelance practice running for 7 years.