Retrospectively casting an eye over an incredible year for both Apple and its customers, one of the most surprising developments of 2010 was the Mac’s long-overdue maturity into a serious gaming platform after years of false hopes and promises.

More surprising than even that, though, is the fact Apple almost had nothing to do with it: even while Cupertino oiled and massaged iOS into a platform capable of rattling the nerves of gaming’s most unassailable colossus, they continued to ignore Mac gamers and its developers.

So who was responsible for the Mac Gaming Renaissance of 2010? There’s no one company in particular, but let’s start with Valve.

On May 12th, Seattle-based game developer Valve Software released Steam for the Mac, a seven year old digital distribution and multiplayer service for Windows PCs serving up more than 1,200 games and boasting over 30 million active user accounts. In itself, that was a significant move, but Valve didn’t just launch Steam on the Mac with a sad cobbling together of extant Mac games: they went as far as to launch Steam for Mac by giving away a free copy of their own AAA physics puzzler / FPS Portal to everyone, and over the next few months, Valve continued to release native ports of their most popular games, until their entire library of in-house games was available on the Mac: the Half-Life 2 series, Portal, Team Fortress 2 and the Left 4 Dead series.

Valve isn’t just some no-name developer. They are widely considered to be the Pixar of computer games, effortlessly blending advanced technology with humor, unique design, excellent writing and soul. By releasing native ports of all of their games, Valve was saying that the Mac was worthy of the attention of AAA developers; by releasing Steam for the Mac — which accounts for 70% of all digital game sales on the PC — they were making it clear that there was huge money to be made under OS X.

Why did Valve make the leap to OS X now though? Why not two years ago? In Valve’s own words, it’s because graphics, for the first time ever, are now a “solved problem.”

For years, the reason Mac gamers were baggage class citizens to game developers had a lot to do with the performance issues associated with Macs. Ever since id software’s Quake debuted in 1996, PC gaming has been driven by cutting-edge 3D graphics engines which demanded gamers to constantly upgrade to increasingly advanced video cards, or — failing that — new software drivers. Because this was largely impossible on a Mac, and because PCs had become ubiquitous, companies naturally developed their games for Windows machines.

Things haven’t changed much on the Mac end in the last year. If you want to be able to change out your graphics card on a Mac, you need to buy a Mac Pro, a massive tower priced and marketed to video professionals, not gamers. Furthermore, since graphic driver updates all go through Apple, Mac gamers have none of the flexibility to try out new driver sets (or roll drivers back) on their machines to see how it improves performance.

But a wonderful thing has happened in the last couple years: PC gaming almost died. At least it did for most the big publishers. Due to a confluence of factors including installed user base, software piracy and the difficulty of supporting so many hardware configurations, AAA games by major publishers are now usually developed for consoles like the Xbox 360 and PlayStation 3 first.Both of these consoles are now five years old… and likely have a few years left in them before their successors are released.

Technologically obsolete compared to the abilities of cutting-edge PCs or even Macs, the Xbox 360 and PlayStation 3’s paltry specs have forced developers who once relied on blistering CPUs, gobs of VRAM and a whole library of advanced shader support to now focus on imaginative and intelligent design. A cutting-edge Xbox 360 game like, say, Bioshock 2 doesn’t look better than an Xbox 360 game released years earlier because it can rely on better hardware: it looks better because the engine it is running on (the Unreal Engine, the same engine powering Infinity Blade) has had years of optimizations and the artists have learned how to design their assets while efficiently leveraging the capabilities of that engine.

What this means is that most PC games are designed to run on consoles, because that’s where the real money is, then ported back to PCs afterwards. As such, PCs that are a few years old are just as capable of running a new game (provided it has been competently ported) as a completely new machine. At least as far as gaming is concerned, the graphic wars on the PC has largely stalled except for the teeth-gnashingly, 3DMark obsessed.

The paradigm shift from graphics to design has made the Mac more viable to game developers than ever. The average Mac’s hardware is now already within the spec window that developers are programming their games for. Additionally, with PC gaming sales numbers so much smaller than that of their console counterparts, any developer who does want to release games for the PC can no longer afford to ignore the Mac… especially as Mac sales continue to meteorically increase month after month, quarter after quarter, year after year.

This is especially true of smaller developers hoping to make a living. While big time publishers like Activision and EA might consider the PC to be “dead” as a gaming platform, the vacuum left in their wake has allowed smaller indie developers to thrive. Their resources limited, these indie developers have tended to rely upon grass roots marketing, focused game design, low system requirements and cross-platform compatibility to maximize their sales audience.

In fact, it’s been indie developers who have really led the Mac gaming renaissance. Consider all of the incredible indie games that have been released for the PC as well as the Mac in the last couple of years… the likes of Jonathan Blow’s Braid, 2D Boy’s World of Goo, Mojang’s Minecraft, and countless more besides. Add to them big name developers like Pop Cap (Bejeweled 3, Plants vs. Zombies) and Blizzard (World of Warcraft, Diablo III, Starcraft II) who have always been friendly to the Mac and what you’ve got is a movement on your hands.

By coming to the Mac, Valve didn’t really start anything that wasn’t already happening, but they’ve clinched it. By bringing Steam to Mac, Valve has re-enfranchised Mac gamers: when you load up Steam, not only are PC + Mac versions of a game usually treated as the same purchase (buying one entitles you to the other), but through Steam you can even play multiplayer games on your Mac against friends on the PC. Not only that, but the Mac gamer also can easily keep up to date with the latest Mac game releases and take advantage of Steam’s aggressive barrage of sales, while the Mac developer offloads the headache of hosting, promotion, marketing and credit card processing directly to Valve in exchange for a reasonably cut of the profits.

All of this happened without Apple themselves doing a single thing to change matters, but that won’t continue: when the Mac App Store launches early next year, there’ll be more games on the Mac than ever. 2010 might be the year Mac gaming truly went mainstream, but it’s only going to get better to be a Mac gamer from here.