Star Trek transporter and Doctor Who's TARDIS are simply "magic doors" with a thin veneer of "science" to avoid invoking "magic". Should we distinguish "hard" scifi (science as an essential part of the story) from "soft" scifi (science used as a setting or prop; the story can be easily transplanted to other contexts)? In that sense, Star Wars isn't really scifi - and even contains elements of "magic" (the Force).

Doraemon is most honest - the どこでもドア (anywhere door) is exactly what it says on the tin.