That is a nearly universal opinion among my acquaintances. Most suggest that Mil Frutas in Rio is competitive with the best too.

Nobody seriously disputes that S.P. has the best Japanese food, including the (in)famous Brasilian-Japanese specialities such as 'hot Philadelphia'. For the uninitiated that is a concoction made of cooked cream cheese with otehr ingredients, formed as if it were sushi. It is much admired by those who like it. For purists S.P. has the only Japanese options that are really good.

Mil Frutas in Rio is certainly competetive with the best.
However, in S.P., there seems to be a sorveteria (ice cream shop) of that caliber on every block. ;-))

That's why I mentioned the name. There are now a couple of others in Rio too, but S.P. is far ahead in choice for all things Italian. Of course we're importing Fasano eateries, Braz and Rascal (for which there is nothing remotely close anywhere else I know) so gradually we're learning from the S.P. italian community.;)

Well, some US cities have a list of best ice cream parlors from contributors to various forums.
Maybe we should start an international one here on FT. :-) Yum! What a marvelous way to tour the world, from one ice cream parlor to the next.

You do have good ideas. as befits one whose proclivities are embodied in your moniker.

For Rio de Janeiro:
Gelato Vero http://www.gelatovero.com.br/#menu-item-2680
Mil Frutas http://www.gelatovero.com.br/#menu-item-2680
Amerena Gelateria http://www.amarena.com.br

There are more...

Yup, hedonist all the way.
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For Salvador:
the famous ice cream shop in Ribeira
the shop at the top of the Elevador Lacerda
local Capelinha brand popscicles sold at various locations (ambulant vendors on the beach shout out the name, pronounced cah-peh-LEEN-ya, little chapel)

Next time you Gelatto experts are in EZE... you need to try

Un Altra Volta
Persicco
Arkakao