On a technical level, yes. It's a meat packed into a cooked yeast, flour and water mix, to which condiments and the such can be applied. However, a sandwich consists of two non-connected pieces of bread, where as a hot dog bun is connected. So technically, yes, but philosophically the same but an entirely different entity. Same as how a phone nowadays has 2GB of RAM, a 2.0 Ghz dual core processor, graphics display chip, display and input devices, but it's a phone, not a computer.