The Ritz on Gran Via is a dreary old place that reeks like a nursing home. Service as I hear it is hit or miss. The location is first rate.
I am not a fan at all of the Arts (aka Ritz Carlton) as it is in the middle of nowhere (well, a touristy strip mall that looks like any American suburb) and far from anything culturally interesting or unique, and the architecture and decoration I think are better left to the fantasies of coke dealers from 1983.
I have before recommended the NH Calderon, mostly for its location and interesting interior, but I will now make a new recommendation based on new information. I recently stayed at the excellent Silken Al-Andalus Palace in Seville and happened to meet one of the company's facilities people who told me about the new property, which I took a look at last week.
The Silken hotel chain decided recently that they wanted to build a hotel here in Barcelona in the style and tradition of the Starwood W hotels, and set out to out-W the W. They have. The Silken Diagonal opened just recently, in the Avenida Diagonal just next to the Plaça de les Glories, a few blocks from most of the tourist sites. The building is stunning, and the design of the public spaces and guest rooms is certainly inspired by the W hotels, but with some local touches and nods to Catalan culture and history. Similar color schemes, Asian influence, funky bathrooms, plasma TVs, etc. Everything finished to a very high standard. As far as service, well, this is Spain, so you won't have an M-O experience here. But it should be very good.
If I needed a hotel in Barcelona I would not hesitate to choose this over any of the other options, including the dreary Hilton, the dreary Majestic, the dreary Ritz, or the tacky R-C Arts.
Did I mention that they have a soft-opening special of 70€ for a double or 130€ for a double on the executive floor bookable through their web site?