If money is an issue (i.e. you don't have shipping containers of it just sitting around) then buying an Apple plain does not make much sense. If we are talking aesthetics and design, Apple is the way to go.
If you have a look at the components inside your Apple machine of choice (iMac), you'll quickly see that a beige/black box with PC components will cost you significantly less, with the added bonus feature of being able to add (more/faster) RAM or a better or a bigger monitor later on. If you have a Full HD TV sitting around and you are happy with a 1920x1080 resolution, you can plug your PC rig in with a five dollar cable, without the need of having to buy adaptor dongles for everything - generally speaking, I don't believe in beautiful machines that have to be spiked with adaptor dongles to make them compatible to available hardware. So, hardware-wise, I really don't quite understand your friend.
The RAM thing I don't get - at all. You're right, RAM usually comes in even numbers: 2GB, 4GB, ... 16GB. With Dual Channel capable hardware, you'd want to buy pairs of RAM sticks, with Triple Channel capable rigs you want to buy triplets of proper good RAM. While it is perfectly possible to have, say, notebook computers with odd amounts of RAM, that is mainly either a failure on behalf of the user (sticking anything in that doesn't blow up is good enough), or the manufacturer communicated the limitations of 32-bit operating systems of old (which basically max out <4GB of any and all memory, video card included)...
The current listings for iMacs I get range from ~$800 (4GB RAM/2.5GHz CPU/500GB HD) to ~$1400(4GB RAM/3.1GHz CPU/1TB HD), so both come with 4GB of RAM. No modern 64-bit capable machine should come with "odd" amounts of RAM, it's just so last century.
There's a chance both come with RAM that is slower than what the machine itself could handle. There's also a chance both machines can be upgraded to the same amount of maximum RAM (8GB/16GB)... these are obviously questions you need to ask if the numbers are of concern to you.
Oh, and about the games... "all PC games are designed on Macs" is right up there with "I did not have sex with that woman!" and Sarah Palin history lessons. The "Put it in! BOOM! Loaded!" is also a rather funky one. It sounds magical, defying reason, logic and fact. There are ways to make Windows software work (perfectly/more-or-less/crap/not-at-all) on OS X, but if you're not savvy with this kind of trickery, there will be a long stretch of tears and sweat between the "putting it in" and the "BOOM! Loaded!"... even if all games were designed on "Macs", they certainly aren't coded on or made for OS X (or Linux, for that matter). All the PC Games I've seen so far come with executable files (*.exe), and your average Apple machine featuring OS X doesn't really know what to do with those. Maybe he meant dual-format install discs, but - as the name implies - installation still has to happen, no matter your system.
The only bit of truth I see can be extracted from "All PC games run on Mac" - apart from the fact that Macs are now generally to be referred to as Apple computers, the fun bit is that they - finally - run on the same CPU architecture as "PC"/Windows computers. So, it is generally possible to install a - properly bought/licensed - Windows OS on it. So, if you don't mind reading up on dual boot installs, and why it might (not) be a good idea to go the official route of using "Boot Camp" (or not), yes, you can run Windows on it and - if CPU/RAM/video hardware and proper drivers allow, you can install and play PC games on it.
So, if you are willing to install Windows (XP or 7, currently) onto your Apple hardware, you *might* have a mostly PC-like experience when it comes to playing old and new games. A big problem could, however, arise with the video hardware inside your splendid new Apple computer, since you usually cannot replace it with something more powerful.
So, as with all hardware cravings, I'd say make sure you know how much money you are willing to spend, then make a list of what you intend to do with it and then find out what best choices are within reach.
Oh, and if you are not too computer-savvy, it is probably a good idea to spend the money on an extended warranty, if available. Just to make sure.