Sophisticated gameplay and cheap downloads that are fuelling a boom in software for smartphones and tablets were on display Thursday at the Tokyo Game Show, the biggest of its kind in Asia.

Developers from all over the world flocked to the town of Makuhari outside the Japanese capital to showcase their latest offerings as the world readied for Friday's first sales of the iPhone 5.

Even the upcoming launch of faster, slicker and more capacious versions of Sony's PlayStation and Nintendo's Wii U, set to go head-to-head in the run-up to Christmas, could not take the spotlight off the ever-improving world of smartphone gaming.

"iTunes store has been the main provider of games for smartphones, but now you can download games that you used to play at shopping mall arcades on this Android phone," said Tetsuya Kamoto at Sony Mobile's Xperia booth.

"As smartphones get more and more sophisticated, the kinds of games you can play on them increases," he said. "But above all, it's cheaper. You can buy a game you used to find at a mall arcade for 300 yen ($3.80) or so."

The industry event opened a day before the iPhone 5 debuts in the United States, Canada, Britain, France, Germany, Australia, Hong Kong, Singapore and Japan.

The latest model of Apple's flagship product -- one of the tech-world's most eagerly anticipated launches -- has a rich four-inch (10-centimetre) display and is compatible with high-speed "LTE" telecom networks.

Apple says the iPhone 5 is "the thinnest smartphone in the world", with a glass and aluminium body that is 18 percent thinner and 20 percent lighter than its predecessor, the iPhone 4S.

"Consoles, PCs and mobile devices have developed separately as game hardware thus far, but in the latest trend PCs and mobiles are getting borderless," said Yoshikazu Tanaka, president of high-flying mobile phone game provider Gree.

"I expect the conventional form of PCs will no longer serve as the main player for game hardware, as they integrate with smartphones and create a new platform," he said. "Eventually consoles will also merge with PCs and smartphones.

"Smartphones have dramatically evolved every year... If this trend continues, they may get even more sophisticated than PCs within a few years," he said.

Japanese electronic games titan Nintendo did not have a booth at the game show, but industry watchers flocked to game software developers who had demonstration versions of the updated Wii U controller way before its release.

"The controller felt a bit bulky," said one-50-year-old, who declined to be named, after trying out the console. "It is not meant to be taken out of home. As long as you stay inside, it's good to play with a bigger screen."

Sony Computer Entertainment will launch a slicker and lighter PlayStation 3 this autumn.

More than 200 companies from 19 states and regions are represented at the glitzy event, which is expected to attract 195,000 people before it closes on Sunday, Kyodo News said.