I have never eaten at CG but I am just wonderfully in love with Narcoossee's. From the moment we walk into the place to the goodbyes we get and give to the staff, it is just an amazing and special experience without any characters or children(not that characters and children aren't great!

)
Opposite experience here. We've been going to Narcoossee's for over 12 years and know plenty of staff there, and from the moment we entered about 2 weeks ago (to celebrate my mom's birthday) to the moment we left, we were completely neglected by our server and given rude treatment for giving a tip
above 20% (because our neglectful server felt entitled to more!). Food isn't memorable compared to the other signatures. And Narcoossee's has plenty of children because it's known more for its view of the fireworks than the food. It's easily one of the noisiest signatures, and the food is rather simple.
On the other hand, I think Captain's Grille is a pretty generic, boring place to dine. I wouldn't really want to sit for a meal there (and last time we had breakfast there, my mom found a bug in her food).
What about Flying Fish? Like Captain's Grille, it's in the Epcot area. And like Narcoossee's, it specializes in seafood. Unlike both of them, it gets really rave reviews.
Or do you mean
California Grill? Captain's Grille is a completely different restaurant and not a comparable experience (especially if you're looking for a date night). If you mean California Grill vs. Narcoossee's, I would say California Grill.