Although this sets out to be a spoof of zombie films (especially the original Dawn Of The Dead), Shaun Of The Dead succeeds on many more levels than that. First of all, it completely nails the essence of the horror/zombie genre, with funny and accurate rip-offs of the stereotype characters and plot devices. Secondly, it genuinely is a “romantic comedy–with zombies.” The love story is honest and heartfelt, with even the peripheral characters being well-drawn and sympathetic. And as a horror film in its own right, the film works. In places it is genuinely scary and claustrophobic. The comedy is exquisitely timed to let you experience the thrill of a horror film before breaking the tension with a belly-shaking joke. It really is an extraordinarily well-constructed film.
Update: see also Tagline’s assessment of it.