Royal Caribbean, known for its mega-ships, is also known for its dining options. The following dining menus from the Freedom of the Seas provide a good indication of the menu diversity you can expect in the main dining room at dinner.
The Portofino Restaurant is available on all RCCL ships but it is a special option with a $20 per person fee. In addition, the restaurant has its own dress code.
Is it worth the extra cost? Definitely, based on my own experiences on several Royal Caribbean ships.
By the way, here is a bit of cruise heresy: dining is usually better on Royal Caribbean than on its sister line, Celebrity, since Royal Caribbean bought Celebrity Cruises.