Daggerfall's schtick was mostly the huge number of randomly generated quests which was pretty much taken lock, stock, and cock from Frontier: Elite 2 and Frontier: First Encounters and other some other really obscure German RPGs that did similar shit.
The huge empty world thing gets boring fast these-a-days, same for the endless dungeons that break 9/10 times. The other schtick was the huge and detailed but decidedly pointless skill system. You could create a really detailed character. none of the detail mattered.
Arena could be seen as grafting Heretic onto Might and Magic. Actually, Arena plays a lot better. No skill system, so less bullshit there. Less buggy. Everything's still pretty randomized, but uh, reasonable. You actually see shit if you wander around in nature even if it's impossible to actually travel between towns (literally -- you have to fast travel, towns aren't connected in a global map). The random dungeon generator could also pop out some interesting things.
Morrowind is sort of less bullshit than Oblivion in that it also tends towards really small and reasonable missions, a somewhat more developed quest structure, and the game environment is DEFINITELY more detailed.
Still, though, Bethesda is DEFINITELY not an innovative company at all.