I'm not a game designer, and I don't even play one on TV, but:
DC 10 - Name of creature
DC 15 - General Ecology - diet, activity cycle, habitat
DC 20 - Combat knowledge - known weaknesses, exploitable behaviors
DC 25 - Specific knowledge - statistical outliers, rare variations
DC 30 - Intimate Knowledge - religious secrets, obscure weaknesses
Aberrations add, say, +5 to the DC, Animals -5, and so on.
One table that can go at the beginning of the Monster Manual, and none of this crap where the more dangerous something is, the less likely anyone is to know anything about it, or where the bigger something is, the harder it is to remember what it's called.
While I understand what you're saying, you're suggesting that someone would recognize a dog, a kobold, a mind flayer, and the terrasque all equally well. While as a DM we can abjucate accordingly, it fits better to scale with HD or CR. I personally have been using CR for the exact reasons given above- "tank" creatures have much more HD compared to CR, where "controllers" like mind flayers have much less HD compared to CR but have more odd abilities to remember.
On the other hand, let me open another can of worms here- Let's say you're facing a 9th level orc fighter. Is it harder to identify this orc as an orc than the 1st level warrior guards? Is it more difficult to identify a 20th level wizard lich than the basic 11th level kind? Obviously it shouldn't be, but technically it is. While it's easy to ignore the character levels when determining knowledge checks, templates become slightly more complex. Liches have a minimum level to become a lich and you could use this, but it's not neccessarily accurate. And vampires need 4HD to become a full vampire and not just a spawn, and then gain a +2 to CR but HD just change to D12s. If you have a troll vampire, what do you learn from what knowledge check?
My suggestion is this:
DC 10+CR= Identify the creature and basic information on the creature. It also reveals the creature's type and if requested basic information on that creature type (humanoids have D8 HD, etc)
DC 15+CR= Common tactics employed by the creature and any offensive abilities poseessed (spell-like abilities of devils, etc)
DC 20+CR= weaknesses the creature has (liches have DR vs silver magic weapons, etc)
DC 25+CR= extremely rare information about the creature.
Also, we need to establish other types of information for other purposes- what do you learn from a knowledge (religion) check to identify religous information. But obviously that is a separate topic.