Disagree. I'm a huge fan of Hitchcock, but the greatness of his films came from Hitch's style of direction, not from any inherent 'greatness' of the films themselves. When film classes analyze Hitchcock, they look at the camera angles, the pacing, the music. Think about all those iconic scenes in Psycho, North by Northwest, Rear Window, Birds, etc.. You can distill those great moments down to specific still images, which is a testament to the strength of Hitchcock's visual stamp. Even his leading ladies had a blonde, wide-eyed sameness to their look and function (won't get into Hitchcock's misogyny, obviously). Hitchcock was a superb stylist who dressed up average stories with elite direction. There's nothing deep about his films, just like none of his films got the best acting out of his actors (partly because he had such little respect for actors).
Tarantino is one of the best film-stylists out there today. Like Hitch, we recognize his visual style the moment we see it. The bold primary colours, the comic-book graphics, the weirdly anxious music. Like Hitch, Tarantino's developed his own canon of famous moments and memes, and his directing style has become a blueprint for tons of directors to reference. And, like Hitchcock, there's no inherent greatness in his films. They're superb eye-candy.
Hitchcock definitely gets the edge when it comes to original vision. Nobody made films that looked like his. On the other hand, Tarantino is an unapologetic fanboy of Japanese and Western styles, and has shamelessly funnelled both genres into his work. But Tarantino gets the edge in stories, obviously because he writes them himself (which I guess falls under a different job title than Director). He also has a big lead when it comes to acting performances. Unlike Hitchcock, Tarantino loves his actors and enlarges them into bigger than life personae. Hitchcock reduces his actors to moveable pieces on a game board.
Bottom line - comparing both directors was something I just mentioned off the top if my head. As I write this post it's obvious their films and the eras in which they're made are radically different, so I'm not reducing the argument down to a simplistic, "Tarantino is the heir to Hitchcock". They're both great stylists, but I don't think either of them have a claim to being among the greatest of directors.