Oblivion fully modded is an awesome experience and it will be even more so 10 months from now. how will skyrim fare against such a juggernaut? some points to consider:
1) it will obviously not have the amount of detail, polish and variety that modblivion has. nowadays this kind of depth can only be achieved by modders it seems, since they are immune from the woes caused by time and money contrains. game developers these day are more and more interested to make the game as good as it has to be to sell, and not a tiny bit more than that. most games that came out in the last 5 years or so have always felt rushed, incomplete, shallow and lazy, oblivion included ( luckily with mods this changes a lot ) , to me. hopefully this will be a bit less of a problem with skyrim, considering bethesda at least doesn't have a completely external entity like EA pressuring them to get the game done sooner rather than later ( look at the shame civ5 is... ) . of course the parent company will not allow them to throw money out of the window, but it shouldn't be as severe as it would be if they had an external producer.
2) I'm pretty sure it's going to NEED modding way less than oblivion. it's probably going to be similar to morrowind in this aspect. go figure, the most popular and best oblivion mods actually FIX the game rather than ENHANCE it. for example OOO/Francesco's deals with the horrible levelscaling. nGCD/realistic leveling fixes the horrible leveling system. unique landscapes fix the boring as hell vanilla landscapes. the list goes on and on and on, there seems to be no limits to the things in Oblivion you can look at and say "what were they THINKING??" ( favourite example here: http://www.youtube.com/watch?v=0wK9dc_O3pM ) .
hopefully this was only due to time contrains and not due to bethesda having become lazy and only caring about money, since it seems they are taking their time for Skyrim.
morrowind otoh felt like a complete and finished, polished product right out of the gate. I've played most of it 1.0 without mods without issues. ( although I did have much more fun with it after adding giants - me loves seeing a huge variety of creatures when running around ) the thought of playing vanilla oblivion unpatched is frightening.
3) how did modded morrowind fare vs vanilla oblivion? this one is a hard one to evaluate since they are very different games... morrowind is way more rpg, has more depth, character and doesn't need many mods to fix its flaws. oblivion is clearly a rushed game, but the action parts are way better, graphics of course, and radiant AI ( not as good as it could have been we know, but still great ) .
my humble opinion is that oblivion still comes up the winner , even with all its horrible flaws. morrowind definitely shows its age, and the combat is atrocious. NPCs standing in place, as opposed to NPCs that walk around, are a big deal for me. but players who enjoy the roleplaying and lore more than me will certainly prefer morrowind still. imo oblivion is a better GAME, but Morrowind is definitely a better RPG ( oblivion is action/RPG. when you look at morrowind combat, I think it's safe to say that the developers didn't think it was very important for the game overall ) with a better story.
4) I think the gap between skyrim and oblivion will be way less than the gap between morrowind and oblivion. same console, and they've said themselves it's an evolution, not a revolution. it certainly looks and sounds that way based on the ingo we've got right now
so, yeah. these are my thoughts. whatcha think? all things considered, which one will be the better game on 11/11/11?