Eating in Rio de Janeiro offers a complete spectrum of eating experiences.  Prices as they would in Paris, London, Chicago range from cheap to very  expensive. You can easily spend $R60-$70 for a pizza and beer. It is an expensive city and the drop in the value of the dollar makes it tougher still. If you are on a buget, there are juice bars nearly everywhere, and some restaurants offer a self service buffet that is priced by the pound ("a kilo"), yes you can find McDonalds and Bob's for burgers and fries or Delirio Tropical pita sandwiches made with anything you might imagine.  The food is hearty and these places are popular with the locals. They are all open air and sometimes noisey but fine otherwise. Also the botequins (bars with sidewalk tables) offer dinner for two for around $50. 

Yes the food at these places is safe to eat as is the food from sidewalk vendors. You will see people selling ears of corn that are large and actually taste like corn. There are also sidewalk sellers or sweets and coconut water and sweets. Also,  Tap water will taste a little like the water from a well chlorinated swimming pool but is completely safe.

Rio's food scene can be divided into several categories; Seafood, Italian, Churrascarias (steak houses), Portuguese, etc.

Seafood

Antiquarius in Leblon has long been considered the best Portuguese restaurant in town, evidence of this is the repeat customers - investment bankers, industrialists, attorneys, doctors (the same crowd that belongs to the Jockey Clube, the Country Clube and Gavea Golf).  The Cod specials are renowned, other seafood is on a par with other restaurants.  It's justly famous for being expensive.

Margutta in Ipanema has a warmer ambience and has a more Italian influence.

Most restaurants offer at least a few seafood options.  Cherne, namorado and badejo are some of the tastier deepwater fish found locally.

Italian

Cipriani at the Copacabana Palace Hotel overlooks the huge pool, has a very good menu and is very expensive, it also tends to have more tourists than locals.

Gero in Ipanema is in the same price range, offering excellet food, impeccable service and shameless wine markups.

Quadrifoglio in the Jardim Botanico area, just blocks from the Lagoa is very upscale and also expensive.

Terzetto, located on the same square as the Sunday hippie fair in Ipanema offers excellent quality Italian-influenced food and the city's best sommelier.

Locals love Margutta in Ipanema, it is elegant, not so loud that you can't have a conversation, less pricey than Cipriani but definitely a place to try, the crowd here are beautiful locals rather than mostly tourists from the hotels.

Artigiano (on the canal separating Ipanema from Leblon) and it's slightly more upscale sister restaurant Pomodorino (on the Ipanema side of the Lagoa) are also good choices.  The former specializes in homemade pastas and offers excellent value; the latter has a somewhat more varied menu.  Both have excellent and reasonably-priced winelists; neither accepts plastic.

Giuseppe (not to be confused w/ Giuseppe Grill) in Leblon is another option worth considering. Some others to try include La Botticella and D'Amici in Leme.

Churrascarias

Pampa Grill downtown is great and by late evening it is a dance club.

Porcao has two locations, the one in Botafogo offers expansive views of Botafogo Bay, Sugarloaf and Urca - more locals here.  The Porcao in Ipanema has no views and is usually packed with a mix of tourists and locals. Rodizio costs about U$ 45 per person.

Marius at the end of Copacabana is renowned for their meats, and the sister Marius in Leme is well known for their seafood.

Those preferring their meat a la carte should check out Giuseppe Grill in Leblon, which is sort of a Brazilian take on an American steakhouse: the model is meats and sides a la carte, but the selections are local.  The beef rib and the maminha are both worth trying.

There are several less pricey churrascarias in Rio. A good option (U$ 20 pp) is Carretão on the Rua Sigueria Campos, about 50 meters from Avenida Atlântica. The quality of the food is excelent. It's quite a small restaurant compared to Porcão an on friday and saturday you will probably have to wait in line to get in.

Portuguese 

If you are a native, "carioca" as they are called, then you love cod, garlic and olive oil.  It would be a shame not to try the  dishes.  You can do it two ways;  dressy and very formal at Antiquarius where the regulars know that like JP Morgan, "if you have to ask how much it costs, you can't afford it".  The preparations are spectacular and the place is always full.

Or if you prefer do it without coat and tie go to the Adega do Portugues where it doesn't matter whether you go to see and be seen or eat.

For those on business downtown, a short taxi away at the Marina da Gloria they will find a Barracuda a very good restaurant hidden away between yacht chandlers and boat brokers.  Don't be fooled, this place holds its own with the others in Copacabana and Ipanema ( order a bottle of Cartuxa Reserve to go with your cod "bacalhau a la portuguesa").

 Belmonte is a series of botequins, one of which is in Leblon. The custom in these establishments is to serve dinner for two. It is relatively inexpensive and the waiter will bring out platters and serve you individually. Do not be surprised to find that the two sides are rice and potatoes. Order and salad and it will certainly be large enough for two.

For relatively light Portuguese influenced food try Carlota in Leblon. It is expensive but the food and service are first rate. This may be the best restaurant in Rio at this time. 

Sushi 

Some restaurants such as Madame Butterfly  in this city are reminicent of those in Tokyo (little NYC decor and no California energy). Madame Butterfly in Ipanema is one of Rio's favorites.

Sushi Leblon is largely considered the city's best and is full of young and fashionable clients, but be prepared to wait if you're not there before 9.

Just down Dias Ferreira from here is hole-in-the-wall Togu, which offers some more exotic options in addition to traditional sushi and sashimi.  (The off-the-menu duck-confit crepe with mango chutney is brilliant.)

Other

For Spanish cuisine, emphasis on fresh fish, there is Shirleys in Leme.

Amir and Arab for Middle Eastern food.

Garcia e Rodrigues in Leblon is a combination deli, bakery, prepared foods counter, wine shop, coffee house and restaurant.  The menu ranges from casual to high-end, mostly french-influenced. It is very expensive and highly prized by the locals. Remember, for years Brazil had the policy of not importing anything that could be produced in domestically. That policy is over and Brazilians are willing to pay a premium for things they could not get. That is what is sold here at prices that are well above the norm for any city.

Nearby Le Cigale, by the same owners, offers some excellent bistrot-style food.

Zuka in Leblon is based around a large open grill on which most of the menu is prepared; the atmosphere is modern and the food is tasty.

Bazzar in Ipanema is another more modern option with a varied menu.

Zaza, also in Ipanema, focuses on eclectic "tropical" cuisine, ranging from Brazilian to Indian to Thai.

Claude Troigois has a place in Jardim Botanico called Olympe, he's the chef du jour and charges accordingly.

If you are wandering downtown on business or sightseeing stop in to Confeiteria Colombo a Belle Epoche tearoom from turn of the century.  Ladies could go there without chaperone for tea and sweets.  Today, besides the beauty of the edifice and its interior you can have a good lunch or an end of day tea and finger sandwiches (maybe finished off with their homemade ice cream?)

Notes on Wines Liquors and Other Libations

If you have a good Chilean or Portuguese wine it can be economical.  If you must have French or American it can get steep.  The same goes for upscale liquor - single malts, brandy/cognac.  If you have a Caipirinha (the tropical drink of Brazil) have one made with Vodka rather than the local firewater, your brain will thank you for it tomorrow.

Off the beaten path

Besides the obvious places, Rio offers many places where mainly locals go. Nice food, mostly typically from the North East can be found on the Feira de São Cristovão or better known by the locals as the "Feira de Paraiba". It's open on friday and saturday nights. Most restaurants will have live music (Forró) and there are two podiums where shows occur, mostly Axé and Forro. Entry is R$ 1 (U$ 0.60).