After Excitebike and Xevious, there are four more to come.
Six 3DS Classics titles have been made for the Nintendo 3DS. Following the release of Excitebike worldwide and Xevious at the Japanese eShop launch, there will be four more titles.
Development on 3DS Classics started at the end of 2009. The latest Iwata Asks has some insight on the process. The games may seem like straight ports, but there is a lot of work in making them 3D. For instance, the first title the team tried was Xevious, but when they made it they realized it looks off to have these enemies shooting at the flying ship from the ground, or having the ship drop bombs to the ground on 2 simple planes.
In other words, there has to be a clear sense of intermediate depth between the 2 planes for it to look correct.