Here are some of my favorites:

Wailea:
Wolfgang Puck (at the Four Seasons)
Mala's (at the Marriott in Wailea)
Longhi's (at the shops at Wailea) for breakfast--excellent, excellent and good service.

Kaanapali/Lahaina:
Kimos
Leilani's On The Beach (Whaler's Village)
Hula Grill (Whaler's Village) -- good happy hour here
Ululani's Hawaiian Shave Ice (why not -- it's fun!)

Out of the way, but worth it:
Mama's Fish House -- (maybe 45 min from Wailea or Kaanapali)