Nintendo did introduce two new franchises to the US with the last generation systems.
Fire Emblem series - two GBA games and a GC game.  Great games.  Tactical RPGs.
Nintendo Wars series - two GBA games, a DS game, and a GC game.  All three handheld games are tactical RPGs that really downplay the RPG aspects.  The GC game (Battalion Wars) is a third-person squad-based action game.  
Both are typically developed by Intelligent Systems (an inteneral development group at Nintendo), but Battalion Wars was developed by someone else and published by Nintendo.  Both have new titles scheduled for the Wii. 
Edit:
There's also Pilotwings.  That was on the SNES, N64, and now it will likely be on the Wii.  Donkey Kong is a big franchise for Nintendo.  And Wii Sports/Wii Play/Wii Music/Wii Motor Sports can kind of be considered a franchise I guess.