Factors included will be price, environment, service, and of course, the opinion about the food itself.
The first location I can recommend is La Rosetta (Via della Rosetta 8-9, Rome). Be forewarned that this is a fish restaurant and only serves seafood dishes. While not rated as the “top” overall, this restaurant which has been around since 1966 (and seated in the same location as a series of other restaurants serving seafood as far back as 1753) is considered to be the top seafood location in Rome, and perhaps in all of Italy. It is not an inexpensive place to eat, but no location serving fresh seafood in Rome is on the “cheap” side. If you intend to eat here, book in advance, as the establishment serves 50 and fills up nightly. The warm season allows another 20 diners to sit out in the garden where the Pantheon can be viewed. The service is overall excellent, with the small staff doubling as wait service as needed. Colors are bright and warm. This family owned restaurant specializes in fresh and local ingredients combined “prepared with genius”.
For perhaps a more popular “top” place to eat, one should turn to Ad Hoc (43 Via di Ripetta, Rome). This location enjoys a 95% recommendation rate nearly universally. Most people who dine here have a good experience. The restaurant is located in the heart of the city, a few steps away from Piazza di Spagna, Piazza del Popolo, and the Via Condotti. The historical building that houses Ad Hoc provides several rooms of dining for up to fifty people. The pride of the establishment is extended to the extensive wine list (over 700 choices have been carefully selected). The food choices are “typical Roman and Mediterranean” but do not let that limit you. If you seek a broad range of meat, fish, and pasta dishes, many of them uniquely local, complemented with the perfect wine, then this highly rated restaurant is perhaps the ideal choice. Prices are considered “reasonable” and the hours extend to one am for dinner only.