I think bethseda should delve into a game including classic monsters such as Frankenstein's monster, Dracula, the werewolf, and the mummy. I think it'd be cool as a gamer to experience a detective, survival horror type of game (like "the evil within") in which players walk through a massive mansion or castle and its grounds exploring the area, fighting ghouls (whatever they may be) and ultimating defeating each monster.
I thought maybe the giant environment could have separate sections each relative to the monster. For instance, when traveling through the grounds of a castle, a player would come across maybe wolves or something creative that fits the theme of a werewolf. At the end of the castle grounds, a player would come across the werewolf monster and have to defeat him only to move onto the next section that is themed for the mummy or the swamp monster.
Plus a game like this could have a great back story. Maybe Dr. Frankenstein has resurrected all these monsters or something. Get creative with the story, get creative with the environment, get creative with ghouls/ghosts/little monsters (maybe from movies) and start this new genre of games. There are no classic monster games besides Castlevania and I think Bethesda would be perfect for creating a classic monster game.
And if it is too much to fit all the monsters, then perhaps make separate games for Dr. Frankenstein and the mummy, etc. But if you can fit them all in one game, then sequels could be fun with different classics or maybe modern horror icons like Jason vorhees, Michael myers and Freddy using the same concept.
I definitely think a classic monster series would be fun if done well. I'd love to experience seeing the classic monsters and fighting ghouls, etc in a well developed environment and I'm sure others would enjoy the experience as well. It would certainly be a breath of fresh air from zombies and games like amnesia, resident evil, silent hill, etc