Games have come of age on the iPhone, and they’re about to get a lot better. The holiday line-up of game titles being released on Apple’s phone shows that developers consider it a solid platform for games alongside other dedicated gaming devices. Nintendo will have to look over its shoulder.

The iPhone 3G’s stunning success in the past 120 days has highlighted the success of the gaming sector. Apple has said it’s had more than 200 million downloads from its App Store since the store debuted in July. Of 8,000 applications on the App Store, more than 1,500 are games. Just two months ago, there were just 900 games. Exact game sales aren’t available, but titles such as Sega’s Super Monkey Ball and Electronic Arts’ Spore games have had the No. 1 spots as most popular iPhone applications.

This is huge progress for Apple, given that games on the Mac have had a checkered history. Just as with other applications, the best games would always come out on Windows PCs or the consoles first, with Mac versions trailing by a year or more. For years, 3-D graphics on the Mac were far behind the 3-D cards on PCs.

With the launch of Windows Vista, Microsoft actually started losing some users to the Mac. EA noticed and launched a policy of releasing many titles on the PC and Mac at the same time. Games on the iPod also took off, particularly with the launch of the iPod Touch, a version of the music player with the same rich multi-touch display of the iPhone.

But Apple realizes that the iPhone 3G is an outstanding game platform, thanks to the multi-touch display, great sound, good graphics, and the accelerometer-based tilt feature. Nintendo’s DS handheld doesn’t have tilt or multi-touch, and its graphics and sound aren’t outstanding.

Nintendo still has a huge edge, with an installed base of 85 million DS units sold versus Apple’s 12 million or so iPhones. People buy the DS as a dedicated gaming device and it’s had hits such as Brain Age and Nintendogs that have expanded the reach of the device beyond just gamers.

Aware of the competition, Nintendo isn’t just reaping DS profits. It will launch a new version, dubbed the DSi, in the U.S. market next year. That version will have two web cams and the ability to play AAC music (a high-quality music file format)  files. Nintendo considers the latter to be aimed at enhancing games, not playing songs the way people do with iPods. Nintendo will have a digital distribution solution, allowing players to buy games and download them via Wi-Fi to the Wii (and then transfer them to the DSi). The DSi will also have a larger screens, at 3.25 inches. The gestures in Apple’s direction are telling.

I know that Nintendo has been worried about this awakening at Apple. In a couple of ways, the iPhone is a better gaming device than the DS. The tilt feature adds the same kind of ease-of-use to the iPhone that the accelerometer-based sensing system has for the Nintendo Wii. And game developers are exploiting the features. Since games developed for the iPhone also work on the iPod Touch, Apple has a sizable market that is big enough for developers to target.

EA has had great success with the five iPhone games it has launched on the App Store, said Patrick Gunn, a marketing director at EA Mobile. The company is launching a new Need for Speed Undercover game in December on the App Store. The $9.99 game has a bunch of tracks and the ability to choose from a number of customizable cars.

Unlike driving games on the DS or Sony