I brought Epic just as an example of an actual competitor actually trying to compete against Steam, sorry if I I was a bit unclear about that.
So lots of entrepreneurs get rich when they make a product that solves people's problems in one way or another and it sells with a profit - let it be a small profit or a large profit. The thing with capitalism is, if you make your profit too large, eventually a competitor will come and provide an equal or better product with slightly smaller profit or they figured out a way to make the product cheaper and still maintain the same profit margin with a lower price gaining a market share.
The problem with Apple, other large tech companies or some grocery chains in some parts of world (this is the case where I live actually) is that they are not allowing a healthy competition in the first place. If a competitor appears on the market, they will buy them before gaining too much traction, or if that's not possible, they will do everything they can in their power to drive them out of the market by lobbying politicians, or if they control some valuable aspect of the market, restrict access to said market.
Valve hasn't practiced any of those shady tactics as far as I know of and that's why people actually think of them as one of the "good guys" even if it is somewhat unhealthy. You shouldn't try to beat down the people playing with a friendly rule set of capitalism because they are the ones driving the competition forward.
I mean Valve has a game store called Steam, but what's the actual position they have? There are competing game stores - both digital and physical - and Valve isn't trying to run their competition out of business with shady business tactics? Just by being good at something and therefore running a successful business shouldn't be illegal or hated by itself - it's the way the business is being conducted that actually matters. Gaben is free to have yacht or two as long as his company is being run with a healthy mindset, their employees are being paid a fair salary (which I guess is another discussion in it's own who decides that) and they are not screwing their competition nor their customers up.