Story highlights Analyst shows Mac vs. PC gap narrowing

PCs outsold Macs by a ratio of about 20-to-1 last year

That's still big, but way down from nearly 60-to-1 in 2004

Factor in mobile devices and Apple pulls even closer

Aside from the iconic (and sadly discontinued) TV ads , the "I'm a Mac" vs. "I'm a PC" battle has never been a particularly close one, at least in terms of sheer numbers. To put it bluntly, Apple gets creamed.

But a leading tech analyst has put together a graphic showing that the ratio of Windows-based computers to Macs has tightened dramatically and is closer than it has been in a decade and a half.

Analyst Horace Dediu of Asymco has been following the Mac-PC war for years and recently crunched the numbers to show that, in 2011, Microsoft's PC desktops and laptops outsold Apple's Macs by a less-than 20-to-1 ratio.

Which, sure, is still lopsided. But it's the lowest margin since 1996 and is roughly the same as 1985, shortly after the Mac was first released. And it's significantly tighter than in 2004, the PC's high-water mark, when it was outselling Macs by a ratio approaching 60-to-1.

Factor in mobile gadgets like smartphones and tablets, where Apple has so far outshined Microsoft (though the Windows-makers hope to change that with the new Surface tablet ) and you've got a playing field that, if not level, is certainly less tilted than it used to be.

JUST WATCHED Battle for tablet supremacy Replay More Videos ... MUST WATCH Battle for tablet supremacy 01:20

JUST WATCHED Google unveils new offerings Replay More Videos ... MUST WATCH Google unveils new offerings 03:38

JUST WATCHED The Number: Google takes on Apple Replay More Videos ... MUST WATCH The Number: Google takes on Apple 01:47

The shift, Dediu wrote Wednesday, began in earnest in 2004.

"Although PC volumes continued to grow, they did so more slowly and the Mac grew faster," he said in a blog post. "What coincided with this was the emergence of portable computing. The MacBook became easily differentiable as a "better" laptop. It was not faster, did not have more storage or any key metrics being used to sell PCs. It was just better as an integrated product."

That's been the biggest shift since the mid-90s, Dediu writes, when the success of Windows '95 gave a similar boost to Microsoft. The PC advantage steadily climbed from 1995 to 2004, dipping only once in a 10-year span.

When iPhones, iPads and other mobile devices are factored in, Microsoft's advantage sits at about 2-to-1, Dediu said, and the two could break even within the next two years.

It's unclear how much he factored in Windows 8, Microsoft's new operating system that will run on both PCs and portable devices with the goal of marrying them together into a seamless computing experience. But Dediu says that Microsoft's evaporating lead could be bad news for the software company.

"The consequences are dire for Microsoft," he wrote. "The wiping out of any platform advantage around Windows will render it vulnerable to direct competition. This is not something it had to worry about before.

"Windows will have to compete not only for users, but for developer talent, investment by enterprises and the implicit goodwill it has had for more than a decade."