you are going to cause the forums to rise up with torches and pitchforks with that kind of thoughts :p
but seriously, D&D, when it started, more closely seemed to be a dungeon crawler, most of the early rule sets had only weapon skills and such, and the first D&D computer games were dungeon crawlers or focused on combat only. I think LoG really fits the RPG better than many newer action games with RPG elements because you can design your party as you want, specializing in the skills you want.
Main difference, in my opinion, between D&D tabletop game and its adaptation as videogames, is that you have an interaction with other people when you're playing the pen'n'paper game. People would often slip into their character's skin and playfully talk to each other as if there were the actual character. You were playing your role, ergo "roleplaying".
That being said, I always felt D&D was quite dull - was it the game, full of complicated rules, or the DMs lacking imagination - but it all boiled down to very simple sessions: Door, monster, treasure, rinse and repeat until biggest monster and biggest reward. Sessions with real, twisted plots are rare... Which is why I find tabletop games like World of Darkness / Vampires more "roleplaying" by relying more on actual story and plot and how the players were interacting with each other as well as the world, than on dice roll and mathematics.
When D&D was adapted, be it Baldur's gate or Eye of the Beholder, the human factor disappeared, and all that was left were the mechanisms ( and, to some extent, the depicted universe ). Hard to tell a story there, even to yourself... Which is why I spoke of the Elder Scrolls games : by being sandboxes, and giving the player an almost completely free control from start to finish, you could be whatever you want. I like to tell myself stories when I play those games. I remember playing Fallout 3 ( ironically the weakest, imo, of Betheda's RPG ) and choosing to be a "bad boy" up to the point I was being tracked by head hunters, where I told myself "I realize I've been too far, now I have to stop and redeem myself. Too bad for Gigaton, I already blew it up :') But let's play a trick on those rich fools up in the tower...".
While you CAN tell yourself a story when playing LoG, there is a huge difference between having your imagination at work and being given the actual mean to do what you want.
But AGAIN, I LOVE LoG ( would I be on the game boards if this wasn't the case :p ), I just think there is a huge difference between Dungeon-master like which relies on gameplay and puzzle-solving, and what I brand RPG which relies on plot and choices.
Edit:
It seems the whole "RPG" term has been twisted over the years, actually.
RPG, as an acronym, stands for Roleplaying Game. As I stated earlier, D&D was encouraging the players to act and do stuff as if they were their characters, in order to create a mood during a session which, strictly from the angle of mechanisms, was maths and dices.
If you remove the human interactions and as such remove the fun in "acting", what is left? Mechanisms. Would that still be a ROLEPLAYING game? I don't think so.
I never heard of the term CRPG, which stands I guess for Computer Roleplaying game? I'd say this term is already wrong. Or what it would imply for the table RPG is wrong. Either it is not a ROLEPLAYING game anymore and as such does not deserves the "rpg" tag, or it denies the ROLEPLAYING part of the table game and dumb it down to mechanics. So for me, "crpg" are not a subset of RPG, they are a completely different kind of games inspired by the technical rules of the pen and paper games.
The same goes for your example of Diablo3, which may have been a derivative from a game which already inspired by tabletop games, but it was not linked to RPG anymore. To the point that Diablo-like games actually got their own genre : Hack and Slash.
That's why I think ElderScrolls are better ROLEPLAYING games than most of the modern (and ancient) production : you got to play your role and do whatever you'd like to do. it's up to the game, acting as the arbiter, to put obstacles on your road, and get the world in which you're evolving to react to your actions. You can help the damsel in distress, sell her to the slavers, ignore her, or even kill her. Up to you.
Games like Dungeon Master, EoB, LoG and co are only centred on game mechanisms and strategy - drawing maps, leveling characters, killing monsters, looting treasure chests, avoiding traps, solving puzzles. They aren't revolving around a particular story, or, rather, the story is just here to set a mood. LoG perfectly understood this and mixed the oldschool gameplay with some modern elements ( the notes, the Dream ) so that they would set the mood they wanted to achieve. But, again, there is no "roleplay" any more. This is a different type of game which should get its own genre, "Dungeon Crawler Game" being the most obvious. It probably didn't get a proper name because it disappeared before given the chance, in an ever-moving world where things needed to be categorized.
But don't get me wrong : my issue resides in the fact that nowdays, a very, very broad selection of games are labelled "RPG" where there isn't any reason to call them so. Again, Final Fantasy and most of the Japanese so-called "rpg" do not have the slightest hint of actual rpg in them, except for leveling and gearing up. I think everyone on this board will agree that there is something rotten there :p
