oblivion's journal only had info on quests. morrowind's journal allowed you to go over the topics you asked people about. the mass effect codex displayed information about the races and other different lore
What made me think of how handy this would be was, I was playing the DLC in Fallout: New Vegas. I read all the terminals and finished the DLC. After you finished the DLC, you weren't allowed to go back. So I was thinking it'd be nice if it had recorded everything that way I could reread everything from the DLC in a journal of some sort since you can't go back.
Morrowind's journal was perfect, it summarizes everything you experienced. BioWare did a good jobs cause it recorded everything, and kept you caught up with the lore as well. Oblivion on the other hand, didn't even have a journal. It had a quest section, and that's it. --- "Don't worry about the motion of the ocean. Lets go fishing, if I've got the notion." - Captain Mike
If you wanna learn about the lore you could always use the Elder Scrolls wiki:
But personally I hope the games never adopt Mass Effect's system. My favorite pastime in Morrowind and Oblivion was building a library, learning the lore from hundreds of different stories and never being quite certain just how much was true history and how much was the author's exaggerations and biases.
For example let's say you want to learn about the earliest history of the continent your on, Tamriel. A Mass Effect style Codex would just let you pause the game and look up an objective, accurate summary of the continent's prehistory. If you wanted to learn about this subject in Oblivion you had to find the one and only book *I think* dealing with that subject, which required breaking into Castle Bravil.
Then you had to gleam what little knowledge you could from the ancient poetry fragments and compare it to what you've read elsewhere to decide for yourself what's true and whats bias and exaggeration. *personally I think the friendly race of bird people who make him their lord and the giant yet easily slain cliffracer are just Topal BSing to make himself look good while the natives are only depicted as savages to fit the High Elf narrative that everyone but them is a savage* --- How I reacted to the news of a new Elder Scrolls game: http://www.youtube.com/watch?v=c9eGtyqz4gY