RustyC

I like La Mar a lot but will do a lot more visits to Punto Azul in Miraflores, which has good portion sizes on the ceviches and of course they're always fresh. Their ceviche oriental (del atun) is my fave. Also hard to pass up the dulce de leche cake for dessert, with prices about half where they are at La Mar. Very popular, though.

La Lucha and to a lesser extent Republica around Parque Kennedy are great with the sangucheria bit, which is arguably a thing in itself. Another "thing" I'll always hit is a roast chicken place, ideally a windowside seat at Pardo's in Larcomar. Like Punto Azul it's inexpensive enough that it's hard to believe it can be as good as it is.

There's also that place in the old-looking house over the water (can't miss it...there's only one like it) that's not cheap but has a really extensive selection of pisco to try.

With Iquitos I liked just about everything at Dawn on the Amazon and most things at the "Texas" place. Thick drinking chocolate and paiche (river fish) were among the standouts. There were also roast-chicken places as fallbacks.