There's no evidence that a portfolio of Basecamps would beat a portfolio of Twitter-hopefuls, and a lot of reasons to think it wouldn't. Most companies fail. They fail when they're carefully run companies on organic growth paths, and they fail when they're reckless moon-shots.
There's an important fact I think people here miss. We tend not to consider a quiet, well-run small organic tech company that generates great salaries for a team for 10-15 years a "failure". And, in the sense that it's lucrative and pleasant and enriching for everyone directly involved, it isn't. But if it doesn't ultimately generate liquidity for investors, it is, for those investors, a failure. Startup investing isn't a charity run by pension funds for the benefit of software developers and product managers, or even for the users who enjoy the products built by those teams. For investment to make sense, it has to generate returns --- not just steady ticking returns, but enough to offset all the other failures.
Companies like Basecamp are great. Incidentally: they're the only kind of company I ever think about starting! But we shouldn't kid ourselves that they should attract investment dollars. Reckless moon-shots are intrinsic to the model of investment-funded companies.