What does it mean by "A good company to work for"?

Any company where your direction is somewhat aligned with your goals is a good company. This alignment is expected to be never perfect. Even your own goals may have conflicts and may not be self aligned perfectly. So being paid little may not be an absolute indication that the company you work for is not a good company, though it may be a factor to consider.

There are many factors come into play and with different priorities for different people.

Factors

1. The people around you are the sort of people you like to be working with, this includes boss, colleagues, subordinates and clients.
2. The work you do match with your interests and capabilities. The work itself is fulfilling.
3. You are paid right. This does not necessarily mean that the highest possible payment would make the company a good company or that a low paying company is a bad one. Also, you are paid on time. Yes, time value of money is a real thing and every one has cash flow requirements.
4. You have job security. People do generally prefer stability, though some people may opt for temporary positions for various reasons 
5. Stability of the organization. Start-ups die fast and easy. Banks are usually here to stay. But risk reward ratio play.
6. Your work environment is enabling. The environment at workplace allows you to work as best as possible. This involves infrastructure and culture.
7. The contract you have with your employer is obliged to. Any deviance from the contract is mutually agreed upon. [Now our (Pakistani) society follows rather ambiguous ways with a lot of room for interpretations. But this does not necessarily implies that the other party is trying to deceive you.  Precision and accuracy are clearly different things.]
8. You have career growth opportunities, also involves growth of the organization. If the company grows and you are a good employee, there are high chances that you would grow as well.
9. Prestige: the company you work for has prestige. Based on preferences.
10. You can preserve your values. Depends upon your values e.g. some people do not like to work for banks for religious reasons.
11. You are valued for your work. Value can be seen by higher salary, appreciations, bonuses, more leverage, or perhaps just right way of acknowledgement.
12. Right level of challenges. There are not too many challenges. Or for some people, there are enough challenges.
13. Right level of maturity and bureaucracy. Again, highly depended on individual preferences; some people prefer highly regular, defined by procedures and policies, organizations, and other go for dynamic ever changing start-ups.
14. Right size. Some people prefer small organizations and some large.

I may have left something, so you may add other factors. Some of these factors are contained within other factors, like being paid on time and contractual obligation may be the same thing depending upon situations. Also, sometimes different factors compete with each other, so you need to weigh them accordingly.

A company is not just the legal entity, nor its just the owners. Employees are very much part of the company and take part in defining it. Also, it is a living dynamic thing, so a company may be great to work for one year and not the better option another year for you, but yet again after a year, it might be very good, if it survives of course.

Another thing to consider is that sufficiently large company may not be homogeneous  one unit or department may be very different from another within the same larger organization. Also when comparing different options, things usually look quite different based on where you are standing. A comparison may not be absolutely objective and true, based on degree of your information or level of confidence of that information. Most people would not get a chance to evaluate every option available in detail. It also depends on your level of career and your ability to switch again that how much analysis you do in comparisons.

As for delayed payments, even if it is true, this might not be as bad as one could think universally. In some companies, specially in IT where perhaps the most important asset a company may have it are people employees are considered assets and many (perhaps not all) employees believe in turn that they are integral part of the company. And both believe that they are not in complete competition with each other and that their gain is maximal in mutual gain. I know about a few companies where employees took the share of the problems, when companies were in hard times they were supported by their employees. Perhaps not every one is always in a position to support. But in good companies employees do support the company at lengths. Even though employers and employees are generally in a competitive relationship, reciprocal altruism may help the everyone overall.