If that's your view of success then many of the web's biggest services aren't successful

Unfortunately, it's a common bar for the continued existence of companies. I'd say successes if the company still offers a service in 5 or 10 years. Unless the operators an employees are all independently wealthy, you need to break even

> Its not hard to define success.

Everyone has their own definition of success. For many, a "successful" tech startup is one that eventually lands a $100M+ buyout, or gets millions of paying customers, or some other metric that's far beyond "simply" arriving at a sustainable business that you (and I) mentioned.