It's well known that Nintendo designer Shigeru Miyamoto isn't someone who rushes. Miyamoto's famous for cancelling, rebooting and delaying projects until they've become something he's proud of. The follow-up to Wii Sports, the game that launched Wii's unexpected popularity, was not decided overnight, Miyamoto revealed during a post-E3 chat with game journalists.
Miyamoto and his team at Nintendo performed a number of design experiments related to different sports that could possibly work on the Wii. He mentioned two ideas Nintendo eventually decided against: Wii Motor Sports and Wii Leisure Sports. Miyamoto did not elaborate on what became of those prototypes, however.
And while Wii Sports Resort comes with a number of improvements over the original -- Miyamoto was disappointed Wii Sports didn't include a way to really improve your skills within the game -- he doesn't consider it a sequel. Neither is Wii Fit Plus. Miyamoto didn't slap a "2" on them for a reason, he said.
It's not like Miyamoto doesn't believe in direct sequels, though; Nintendo announced development of Super Mario Galaxy 2 during their press conference.