Free software is code that is not encumbered by copyright or intellectual property rights. From the point of view of its creator, it is something he offers to the community without guarantee, for the community to use and to improve on. From the point of view of the community, it is free for use and for modification.
It is indeed arguable that free software is superior to proprietary software. However the model being used by proprietary software leads to impractical situations. If I have a copy machine using a non-free code, I won’t be able to modify the code to better suit my particular need. I would have to buy another one for this one utility and use the former for the rest, increasing my cost. If I happen to be a programmer I still can’t modify the code because somebody else owns the copyright. If the non-free code is failing/showing a bug and I happen to be a programmer I cannot just modify the code, again because of copyright.
Proprietary software is essentially a monopoly that is anti-progress and so impractical when applied to the software world. It is a yoke carried by all non-free software users. Now I don’t believe that there is a direct correlation on quality and free software. What I do suggest is that the free open source model is better at delivering technology to solve our problems.