I’ve seen them all and Reservoir Dogs is without a doubt the best for me. It showcases in full display the creative dialogue and film execution that Tarantino would use for every film he’d do afterwards and honestly the great values and high quality of these elements when used in such a self-contained low budget film always gets to me, its always exceptional to pull this off.
Pulp Fiction and Inglorious Basterds would be my second pick, both fantastic films. Maybe Once Upon a Time would be next, I haven´t given much thought to it, but the rest of them follow after these. I don’t really think he has done a geniunly bad film to be honest, even Death Proof which is the one I’d consider his worst is still decent all in all.