1 game split into 5
The Tomb Raider Anniversary edition has recently been released on PC and PS2, with a PSP and Wii version on the way on the summer. It was looking as though the Xbox 360 wasn't going to get a look in, but according to the official ESRB (Entertainment Software Rating Board) website, it appears that Eidos will eventually release the title on the console, in episodic content.
The ESRB are about as official as it gets in the gaming industry, so it seems unlikely that the information stated on their website is incorrect. The site currently shows five different Tomb Raider titles, all of which cover the areas that you'll find in Tomb Raider Anniversary, which suggests that Eidos will be releasing each episode separately as Xbox marketplace downloads.
The five titles are Tomb Raider: Anniversary Croft Manor, Tomb Raider: Anniversary Egypt, Tomb Raider: Anniversary Greece, Tomb Raider: Anniversary Lost City and Tomb Raider: Anniversary Peru.
The website gives no indication of release date and we're still waiting for an official announcement from Eidos.
Source :: ESRB