At the 2011 Tokyo Game Show, the main attraction is Sony's PlayStation Vita.
Sony's massive layout dominates the show's floor, with 70 Vitas available for hands on trials, and on opening day attendees lined up for over an hour for a few minutes with one.

But right next door with an equally impressive booth is Gree, a Japanese online game publisher. Gree mainly makes games for mobile phones, and charges for subscriptions or advertising. The company is already dominate in Japan, and its large presence at the game show comes as it aggressively pushes abroad.

Gree began with simple games for mobile users, but is now teaming with major publishers to create in-depth titles and social networking games. This could pull gamers and developers away from the Vita.

In hardware, the Vita's main competition is the Nintendo 3DS, which launched earlier this year. Both devices are aiming to draw a broad range of users as well as traditional gaming hobbyists. Nintendo didn't come to the game show, but other hardware was on display that could attract more casual gamers away from the 3DS and Vita.

The Sony-Ericsson Xpedia Play, a mobile phone which slides open to become a controller, will go on sale in Japan in October or November. There is an ever-growing market for games built around Apple's iPhone and iPad remain a challenge as well.

Smaller developers that are hoping for a hit on the Apple devices came to the Tokyo Game Show from around the world. So there will be plenty of non-traditional challenges for Sony's Vita. Sony's Vita is due out December 17 in Japan, and next year in the US and Europe.