Kapalua: Cane and Canoe at the Montage (down the road from the Ritz) is good as is Merriman’s (a bit further down the road). I like Sansei as already noted above. They have another location in Kehei, too.
Lahaina: Honu (Mala’s sister restaurant and next door neighbor) is one of my favorite restaurants in Maui.
In Wailea: The Restaurant at Hotel Wailea is excellent. Gannon’s is good. Monkeypod is fun for lunch.
Other: I really wanted to try Nuka but didn’t make it on my last trip. I had a wonderful lunch at The Mill House at Maui Tropical Plantation.