There are a few nice additional Chinese typefaces in Mountain Lion, considering the cost of buying these fonts separately, upgrading to Mountain Lion is a tremendous bargain.
Most of these new fonts are not enabled by default and will only start downloading when you enable them in Font Book. Speaking of which, Font Book is updated in Mountain Lion, the typeface sample layout is improved.
I didn't include Japanese typefaces in OSX which are CJK fonts, they include extensive Kanji characters or Traditional Chinese, but without Simplified Chinese characters.
I'm not able to show the original size here, but you can download the original size image here (336 KB), choose "Actions" > "Download photo".
UPDATE: Apple list of all the fonts in iOS 6, and interestingly what additional typefaces you can optionally install with your App, a lot of the fonts listed here is in the optional table.
UPDATE 2: Mavericks added 2 additional Chinese typefaces, both hand written style and very good looking ones for both TC and SC versions.
苹果 OSX Mountain Lion 所具有的中文字型。不过大多需用者重 OSX Font Book App 里下载，绝对不难。以下图表最大版本下载，请选 "Actions" 然后选单里单击"Download photo".