Just came back from a great 10 day stay in this amazing city. Like every major city there are a lot of pluses and a lot of minuses, but all in all a destination I would definitely return to.
Generally speaking you have to love meat, salt, dulce de leche and ice cream. If you are vegetarian you will be hard pressed to eat a lot of variety.
Oviendo (Recoleta) -- one of my favorites. Classic Argentine with a twist. One of the few places that actually had fresh fish and did it well. The atmosphere is high end bistro. Great night out.
Resto (Recoleta) -- Another winner within the Architecture Society building. Good clean flavors. The best sweetbreads were had here.
La Parrilla Pena (Centro) -- Hole in the wall Parrilla. Nothing fancy, but sometimes that is what is called for. Everything we tasted was delicious with exceptional meat.
Sarkis (Just north of Palermo Soho) -- Some of the best tasting Middle Eastern food I have tasted. Fresh flavors. Not fancy. A great spot for lunch after shopping in Palermo Soho.
El Sanjuanino (Recoleta location) -- Best empanadas on this holiday. Stick with the empanadas and you will not be disappointed.
Cabrera Norte (Palermo Soho) -- Yes, it is full of tourists. But what they do they do it well. A great evening well spent. Although their estimated time for our table was about 1 hr less than the actual. They gave us bottle of Chandon as a sorry. Nice touch.
Chez Nous (Recoleta) -- Classic Argentine with a French twist. Very expensive for Argentine standards, but the meal could have rivaled ones I have had in NYC or London. A beautiful dining room as well.
Have a Choripan in Puerto Madero along the Costanera. You will notice one place across the street with a glass enclosure. Most locals were going there and I can vouch that it was delicious.
Best chocolates were at Vasalissa (a few locations).
Best ice cream was at Volta (various locations) + Arkakao (Recoleta)
Have a coffee at La Biela...more for being there outside that the actual coffee
Milion(Recoleta) -- go to the second floor bar or outside patio for pre-dinner drinks.