Okay, but realize that not all software is in a critical missions role. Is it worth paying $100 dollars to be sure the game you bought last week won't occasionally need to be shut down and rebooted? Do you need the office suite with super critical testing that costs $1200 for the package? Different situations call for different criteria. The best evaluation system on the planet, IMHO, is called Open Source. There is no hiding a bug, booboo or kludge here. The price says everyone is using it and testing it on the widest set of platforms possible. And for fun, you can fix it yourself if you think you can do better. Besides, if everyone did everthing the same way, we'd all make our living in the aerospace industry and starve because no one farmed. Just my two cents worth.

You start out with a simple question but then, elaborate with more complexities.
In my estimation, any software you design will only be reliable if I don't need to depend upon it.