Morrowind and Oblivion were both incredible games, each with a very different feel and play style. For all their good and bad points, they were hugely ambitious games that have stood the test of time, and have changed the way we role-play forever. Moving forward with Skyrim, which elements of these and other Elder Scrolls titles would you like to see brought to the table, and how would you like to see the Creation Engine and other new tech really show them off and bring them to the next level?
From Morrowind - the atmosphere
From Oblivion - the much more visceral and tangible combat system, and the much more interesting quests
Didn't play Daggerfall or Arena, but I understand Daggerfall had a lot of random generated content - don't want that, give us more hand-made marvels instead.
As for the rest, it's all just details that don't make a huge difference. EDIT: Though I would really be annoyed if there were no magicka regen.