Seafood mostly sucks in Buenos Aires which is a shame. I totally agree with you that it is just not good for a city of its size.
Osaka by far is the best seafood in the city but as you mentioned, it's expensive. My other favorite is
Restaurante Lima Estilo Nikkei Pacheco. It also isn't cheap and you can easily drop a few hundred dollars there with 2 people. But the quality is very high. Service last time was very slow but ask for Alexander. He is the best server there and a very funny guy.
There are only two truly good sushi places in Buenos Aires. The best one is Osaka and the second best one is Restaurante Lima Estilo Nikkei Pacheco. I’ve been coming here for many years. I used to live around the corner from this restaurant. I lived on Avenida Alvear / Rodriguez Peña...
www.expatsba.com
I also like
Picaron which has some seafood dishes as well. The menu is always changing. But they usually have some seafood dishes. Everything is very high quality there and prices are reasonable there. But it's always packed so make reservations or you won't get in.
This is one of my favorite restaurants in Buenos Aires. The food is really delicious. You MUST have a reservation as this is one of the only spots where there will be a line out the door at 8 PM. 75% of their bookings are by reservation and they do 25% walk in. I always have an 8 PM...
www.expatsba.com
Gran Dabbang often has some seafood dishes.
Crizia and
Roux also have some seafood. Some people like
La Pescadorita but I don't think the seafood is that great for the prices that they charge. It's around the corner from one of the apartments in Palermo Hollywood that I own. It's ok and maybe the largest selection of seafood besides the ones I mentioned above. They sometimes have a good fresh catch of the day.
For me, I hate paying mediocre for mediocre seafood in Buenos Aires. I'd rather pay more like at
Osaka, La Mar, Lima Estilo and get GREAT seafood.
I agree down in Patagonia they have amazing fish. One of my favorite is the Trout down there which they have in just about every restaurant and mostly freshly caught that day or the day before. Also, in the South they have this crab called Centolla that is absolutely the most delicious but I think it's seasonal. I get it every time I'm down there.