I am the same as you: I enjoy gaming on OS X, and I don't think I've come across a game that I couldn't play (excluding The Witcher, which had a horrible WINE-based port and was very unstable). At the same time, I recognize that I'm being somewhat selective about what games I'm even trying to play.
Macs and OS X can be used for gaming, but anyone who wants to primarily game with their computer is doing themselves a disservice by getting a Mac. Software-wise, nearly all games are released to Windows first, if not exclusively, and hardware-wise most PCs have the upgradeability so that you can keep up with the graphics update cycles to play the latest, most demanding games and get the most out of them. The way I interpret it when people say "OS X is a poor gaming platform" is that it's a relative comparison, rather than an absolute - that OS X can be used for gaming, but at this point in time it's not the optimal solution to go with.
That's fine for older guys like us, who are probably using their Macs for gaming only a minority of the time they're on the computer. I don't think it's satisfactory or a good use of money for someone who wants a machine primarily for gaming, though. After all, a tractor trailer can serve the role of a commuter vehicle, but that doesn't make it a good choice for the purpose; rather, I'd think it a poor choice. Similarly, I'd say that Macs and OS X are a poor choice for someone looking primarily to game, at least at this point in time.
There I would not differ with you. For a computer gamer who's primary use of a computer at home is gaming, a Windows PC is the obvious choice.
For me owning Apple products that work beautifully together in concert providing a great deal of functionality that extends beyond gaming is important. So too are the broad array of specialized apps available. It is easy for me to put together a suite of apps that perfectly suit my own personal needs on the Mac and I love that. I love the elegant user interface of OS X. I also love the elegant space saving design of the iMac and how it is whisper quiet most of the time.
There were two things that kept me in the PC world for a very long time. First and foremost was my work and secondarily computer gaming was a plus so I bought hardware and built my own systems accordingly. I needed to run Windows and Linux at home so there was nothing to think about. Later when that was no longer true, gaming both in terms of hardware and software was the issue holding me back from switching to Mac for a long time.
By 2012 though things had improved so dramatically on the gaming front that I finally took the plunge and got a mid-2011 iMac while everyone was waiting on a refresh that didn't wind up coming until the end of the year with some orders not being fulfilled until early 2013. Wouldn't you know it, I had to pick a bad year for iMacs where some of the 27" models had serious heat issues. It was a very good thing I went with Applecare since I had reservations about a system I could not easily service myself. The thing wound up running so hot while gaming it literally and I am not making this up, melted the display including the glass cover. I am lucky it did not spontaneously combust. The GPU failed of course with this abuse as well. Finally the hard drive started to go. After three in home service visits replacing displays and various other components that also included the DVD drive and one other thing I am forgetting now I suggested that it was time to replace this lemon.
I was very pleased that Apple immediately agreed with my assessment that the situation was hopeless and shipped me a brand new late-2013 27" iMac complete with an external Superdrive so I would have no loss of functionality and a GPU upgrade for free as well. Downtime was about one day as they shipped overnight immediately once they had confirmation of pickup of the old system here which they send a prepaid overnight label for as well. The whole process was painless and cost me nothing. The best part is they refunded the balance on my outstanding Applecare time and offered me several alternative warranty options for the replacement system. I took the option of a free year standard warranty with option to add Applecare at any time during that year. I am approaching the time I need to buy Applecare again now and I will although this time around has been completely trouble free. I want to know for another two years that I am golden if any issues arise.
I got into all of that because that kind of warranty service and support has real value to me. I do not want to diagnose and fix computers anymore just as I don't want to climb around under my car fixing it anymore either. Those days are over. I had my fun and then some.
So for me an Apple computer means a whole lot more than simply gaming. I consider the software such as Time Machine and other included apps to be a significant value as well. Time Machine made the transition from my old iMac to the new one completely painless. I could not believe how well it actually worked. I was up and running with exactly the same environment I had on the previous system in a matter of hours. It was a beautiful thing.
I think my point of view is often lost in these sorts of discussions where the focus is squarely on one facet of Mac use. Some folks don't want to hear it but an appropriate choice of Mac with a decent mobile GPU does play many games well enough for a lot of us and the options of Parallels or Bootcamp are there to access Windows games as well if desired. There's no problem getting solid midrange performance with appropriate hardware choices.
All that said, once again I truly do understand and agree that if the focus is purely gaming, midrange performance in the PC world can be had for far less money or for the same money high performance can be had particularly when you build yourself. I want a lot more out of a computer than this though and for me Apple delivers the goods like nobody else. That to me is worth paying a premium for despite being constrained to midrange gaming performance. It's not like I ever spent on the PC side for better performance than that anyway. I didn't think the difference was great enough to justify it.
I hope gaming performance gets even better but I will never expect nor need my Mac to be on par with a Windows gaming rig. I think anyone wishing for this is just banging their head on the wall. Apple doesn't make gaming rigs.