Namco Bandai Games have released an app on iTunes that brings some of their classic games to iPhones and iPads. Currently, only four of their games are available in this virtual arcade (Xevious, The Tower of Dragua, Motos and Phozon), but more Namco classics are to be expected in the near future.
Each day, you can play one of the games in the arcade for free, but if you want to play more you will have to acquire some virtual coins first - or permanently unlock each game at a slightly higher price.
Relevant link: Namco Arcade (iTunes)