Of the many Nintendo franchises on hold, none seem to have as much history and as much reason to be made again other than the Advance Wars series. First, let us note that calling it the Advance Wars series is an inaccuracy; it should be more correctly referred to as the Wars series. While the franchise is most well-known under the Advance Wars name, it actually preceded the start of that sub-series by more than fifteen years, first releasing on the Famicom as Famicom Wars.
Regardless of its origins, what fans of the series like, what the natural continuation of it should be is in the style of the Gameboy Advance and Nintendo DS games.
The franchise is mainly a turn-based tactical strategy (TBTS) game made primarily by Nintendo’s Intelligent Systems (IS), not unlike their famous Fire Emblem series. While it doesn’t utilize the RPG elements of Fire Emblem, Advance Wars requires more strategy.
Source: Destructoid Where the hell is Advance Wars?