There's something about a grouper filet that defies the worst efforts of the worst cooks to make it bad.
Perhaps the grouper sandwich at Rick's (on Roatan) has an edge in that their commercial fisherman/supplier is a regular there and, as such, ensures the very first order of prime quality and freshness, while the proprietors, as ex-commercial-fishing people from NE, have an unusual abhorence for messing up a fine piece of fish. I wouldn't stick my nose up at any grouper sandwich that I've eaten but this one, to my palate, has decided edge. There's nothing really extroardinary about the peparation concept but the result highlights the exceptionally fine fish rather nicely.
The only weakness, now that you've brought it up, concerns the quality of their sesame seed bun, although it's the very best they can get here on an island where the quality of available bread products is generally dismal.
The quality of the lettuce and tomatoes typically available here is also quite dismal (and suspect) but they obtain both in very high quality direct from a hydroponic operation run by a local expat.
The tartar sauce, which is in the NE-style, is worth mentioning only because they get it right on. I find most bottled varieties a little
too mayonnaisey, or even MiracleWhipy, for my tastes while homemade offerings often either add too much onion (instant burp city for me) or other clever additives that, while sometimes not bad, end up masking the taste of the fish.
You almost can't ruin a pork chop, for me, but I tend to be a bit of a purist when it comes to fish sandwiches, scrambled eggs and Martinis -- but that's another forum.