We just spent two nights at Grand Hotel Santa Lucia. It's located between Vesuvio and Excelsior on the waterfront across from Castello dell'Ovo. Location is very nice. It's rated 4 stars. Our room (we wound up in a sea view junior suite on the corner) was renovated and pretty nice. I'd say the room was 4 star quality, while public spaces and service (competent but very cold) were really 3 star. Breakfast was serviceable, with an upcharge for a la carte options (which we did not try). For those with any sensitivity at all to scents, housekeeping uses a very strong, chemical-smelling "air freshener" which we found overpowering and which resulted in our rejecting the first room assigned (second was much better).
Pricing is ridiculous, which seems true at pretty much all the higher end options in Napoli right now. This place was absolutely NOT worth the 625€ per night we paid for an executive sea view. (For comparison, Vesuvio was pricing at 1200€ for deluxe sea view, while Romeo was 800€.)
Overall we did not like Napoli and would not return.