Honestly, I really like what Star Wars had done as the Expanded Universe began to balloon. They had to establish a system to keep everything straight, and they ended up with a common sense approach.
In decreasing scale of "canon priority"
1) Anything said in the films is absolutely inviolable unless knocked down by a later film.
2) Below this, Television programming (with the written exclusion of the Holiday Special because everyone regretted making that) could only be superceded by a film.
3) Here you have the "Recent Works" canon, which is probably the shiftiest layer. Consisting of all recent works (and many older works) released under the name of Star Wars: books, comics, games, cartoons, non-theatrical films, and more. Games were a special case, as generally only the stories were canon, while things like stats and gameplay may not have been; they also offered non-canonical options to the player, such as choosing female gender for a canonically male character. Some of these elements have appeared in the movies, making them Tier 1 canon; examples include the name "Coruscant," swoop bikes, Quinlan Vos, Aayla Secura, YT-2400 freighters and Action VI transports. In this layer, only the most recent work to address a subject would be considered canon: a 1994 novel and a 2001 novel which conflicted would have canon precedence given to the 2001 novel.
4) Secondary Canon; these materials were available to be used or ignored as needed by authors. This included mostly older works, such as much of the original Marvel Star Wars comics, that predated a consistent effort to maintain continuity; it also contained certain elements of a few otherwise non-canon stories, and other things that "may not fit just right." Many formerly Secondary canon elements were elevated to Recent Works canon through their inclusion in more recent works by continuity-minded authors, while many other older works (such as The Han Solo Adventures) were accounted for in continuity from the start despite their age, and thus were always recent works canon.
5) Detours Canon, used for material hailing from Star Wars Detours.
6) Directly non-canon. What-if stories (such as stories published under the Infinities label) and anything else directly and irreconcilably contradicted by higher canon ended up here. This was the only level that was not considered canon by Lucasfilm. Information cut from canon, deleted scenes, or canceled Star Wars works fell into this category as well, unless another canonical work referenced it and it was moved to a higher level of canonicity.
Now, Castlevania is FAR from that mangled, but if you like, you can use this as a baseline for your own interpretations. For me, I'd probably put (with heavy thought given in each case) clarifying interviews and such probably about where Leland Chee put TV shows in terms of canon: as it comes from a primary developer, it's probably fairly solid, but cannot in any instance take precedence over what is said or shown in a game.
So basically, a Castlevania scale could look like this:
1) Games that fit in the officially endorsed Konami timeline take precedence over everything else, full stop.
2) Manuals, Developer notes, interview comments and clarifications
3) Novels, comics, or other spin-off media, giving priority to more recent works
4) Elements of non-canon games that do not conflict with any of the above in any manner
5) Pre-canon materials (anything Konami might have missed while Iga was building an official timeline for them)
6) Noncanon materials which DO conflict
6.5) Pachislot shitstains
It's not perfect, and as loathe as I am to accept anything outside the games as canon in any way, just going by that basic structure is probably gonna help iron out a LOT of arguments before they start. Feel free to agree/disagree in your own time with this. I certainly do. But for civility's sake, I think we need to have some basic rules of priority as far as canonicity goes for debate and discussion and this seems to me about as agreeable as anything else that might be put forward. Some rules to play, by just to stop auto-gainsaying in discussions.