Oblivion kept my loyalty over Morrowind by being fantastic in the main areas I bought the game for: ARCHERY! Plus ALCHEMICAL POISON MAKING! Plus STEALTH!
Elven arrows, fletched with eagle feathers, arcing silently out from hidden nooks, their bladed broadheads sticky with homemade death in a variety of exciting elemental and non-elemental flavors....
Ahem. Yes, obvious Dark Brotherhood fanboy here. The Morag Tong just didn't do it for me, sorry.
My primary concern with Skyrim, aside from the lurking dread that it's going to secretly bite rocks, is the loss of the "jump" skill. I'll admit it was easily abused level up-wise....
"I'll just, you know, skip all the way from Bravil to Anvil. In full plate. Because that makes total sense. La! [clank] La la![clank clank] La lalalalala.... [clank clankity clank clank]."
However, it also made lightly-equipped wire-fu characters possible, especially in Morrowind, where it really got ludicrous. Even in Oblivion, the Shivering Isles expansion, otherwise mediocre, was brilliant if you packed light, maximized Jump, and took shameless advantage of the unorthodox terrain. Giant roots became bridges, walls became walkways, and many a dungeon became an exercise in puzzle-solving rather than a mere collection of hack-and-slash encounters.
Hell, for that matter, Oblivion gates handled as wire-fu stealth/speed runs turned from repetitive, monotonous slogs into lightning-quick exercises in tactics, timing, and judicious use of your few precious invisibility potions (leveling up Illusion so as to have Invisibility on tap is, I assert, strictly for game-breaking pansies) that could be finished in minutes and handed you, over time and at random, some of the most powerful magical effects in the game courtesy of your rapidly-accumulating collection of Transcendent Sigil Stones.
Ah, vividly do I remember sheltering temporarily on a narrow ledge, leaped to in desperation to escape the throng of fearsome Daedra, mad with blood-lust on the walkway far above-- then dropping, silent as a leaf, back into the corridors of the black-walled citadel to make my cautious way back past the frustrated horrors that had so nearly torn me limb from agonized limb....
*sniff* Skyrim is losing one of my favorite skills.
Still, looking forward to it, and have it on pre-order. Will be playing a Wood Elf archer/assassin, most likely. I may even play a guy, now that Wood Elf males no longer look like slightly-oversized hobbits.