I'm not sure they ought to be Mario-branded, but with EA Sports blacklisting Nintendo platforms, the company really should make its own dedicated sport games with more depth and character than a Wii Sports compilation. It shouldn't exactly be a sim, but it should have almost as much content as a sim, and it should avoid the pitfalls of EA Sports' better Wii outings.
In particular, don't include a levelling system, or at least tone it down. Most of the complaints of bad WM+ controls were due to the computer adding "noise" to the input to simulate a low skill level when the player starts. This is important when sports skills are simulated with a binary button press, but largely unnecessary when they're derived from infinitely more complicated motion controls. As you learn to swing the wiimote with more accuracy, you'll naturally "level up" without the computer's help.
"The worst part about these reviews is they are [subjective]--and their scores often depend on how drunk you got the media at a Street Fighter event." — Mona Hamilton, Capcom Senior VP of Marketing
*Image indefinitely borrowed from BrainBoxLtd without his consent.