I can't comment much on Oblivion really, since i played it for about ten minutes before i was epicly bored of the game.
I hated the sheer size of the landscape, even with a horse it was boring as hell to get around and fast travel just sort of killed it for me.
I want a world i could walk across, not hours of green forest.
If there was any kind of fast travel at all, make it like the silt striders, i really enjoyed that system compared to Oblivions "click and go".
Make it less bland, from what i saw, that being preciesly "One of the portals into Oblivion" "Some kind of hellish place, guess that would be oblivion eh?" "One town" and "Some place with holy folk in it" (didn't seem church-esque)
I can say, after waiting with the patience of a saint to play that game it was a slap in the face. One of those "is this it?" moments that i won't be looking forward too again.
Whilst Morrowind granted only had dry mud and grass patches with the occassional spot of sand, the world was still pretty intresting, especially jumping over to Solesthiem for the first time.
I didn't want to walk the landscape, and that's pretty bad for a player who doesn't like fast travel to actually want to use it.
My gripes mostly tie in yes, but still that was what killed the very limted time i spent on Oblivion for me.