My favorite hotel bar in the world? Whichever one I happen to be in. Beyond that, I reject the question. The question misses the point entirely. The key thing about a hotel bar, any hotel bar, is that it doesn’t matter where it is. That’s exactly what distinguishes it from a bar that is not a hotel bar.
Take, for the purpose of comparison, the Brooklyn Tavern. The thing about the Brooklyn Tavern is that it is, as the name suggests, in Brooklyn. And not only that: It’s on a particular corner in Brooklyn, the corner, to be precise, where the Brooklyn Tavern is to be found. The only way to be there is to be on that exact corner of Brooklyn. That is what I mean by a bar bar. Whereas a hotel bar can be anywhere (just now the Riad El Fain in Marrakech, as it happens).