Reservior Dogs isn’t a remake of City on Fire. While I will admit it takes some major elements from City on Fire, it would be discrediting to not only Tarantino but the other films he borrowed ideas from to call it a remake of City on Fire. Some large film influences are Le Samourai (the tree way showdown), and Taking of Pelham 1, 2, 3… (the costumes and names such as Mr. Brown and Mr. Blue). Other smaller part come from The Wild Bunch (which the slow motion walking to Little Green Bag was a homage to), The Killing and Rififi.
If you want to be specific you could say some scenes were remade, such as the Crook vs. cops in car scene (where the crook shoots the officers with two guns), but the film on a whole is a completely original experience and movie.
Finally to call a film a remake is in no way insulting that movie. Take The Maltese Falcon for example. An absolute masterpiece. Also a remake. Not only a remake, but a second remake. (The version you are familiar with was released in 1941, whereas the original version was released in 1931).
