My personal favorite is Oblivion, though in all fairness, I have played over a 1000 hours on Steam and XBox on Skyrim, I only got that far because their is a more powerful modding community in Skyrim when compared to Oblivion, easily doubling since the stats on Nexus mods are 16,000 for Oblivion and 40,000 mods for Skyrim, which really helped you play the game better.
Though the reason I believe Oblivion is superior to Skyrim is the way it was presented, and by that I do not mean Graphics, (Though Skyrim is too pretty.) I mean the quests were engaging and enjoyable, as well as repeatable and I can't name anyone who forgot the Murder House in the Darkbrotherhood Questline, though when compared to Skyrim the quests felt. Well simply dull. A grind through the quests are somewhat tedious, an example being the Winterhold Questline as well as Companions, the Companions, lets face it, everyone joined that because they could be a werewolf which novelette dissipated quickly. And Winterhold was a dull walk through of a overall dull questline, I don't know what it was, maybe the
Eye of Magnus just didn't have a very strong pull to it, on top of that people who didn't explore the lore would simply think, "Pretty."
The Dark brotherhood Questline was also simple, (A pet peeve is how the Night Mother regained her skin.) simply gifted you with the title of Listener early on and then you just get a bunch of constantly dull radiant quests. Which seaways into the Radiant Quest system, something I am starting to fear is going to be a staple in Bethesda works. It feels they use radiant quests to substitute real interesting Questlines, it takes away from a big chuck of the Elder Scrolls game which is the lore they have so delicately weave and it takes away from content and I feel they focused on pretty colors.
On the situation of the Notorious Guilds lets go onto the topic of the Theives Guild! Something that was somewhat interesting in Oblivion but in all fairness I was not much of a sneaky sneaks sneak, but it was at the very least an interesting in oblivion, in Skyrim it was... dull at best. I mean, the radiant quests to restore the guild was the most repetitive thing ever to have to deal with. It is one of the only achievements I don't have for the game on steam because it is so repetitive and would honestly rather play a flash game then that long and boring mission, though the Septims are good for what it is.
Now then, let us do a little comparison of the DLC's in Skyrim to Oblivion. Oblivion had 9 DLC's though we will stick with the proper content ones, so it will be Dragonborn and Dawnguard VS Shivering Isles and Knights of the nine.
So little recap on Shivering Isles. It is wonderful, the creatures are engaging the quest manages to do what Sheograth is good at, be both able to taken seriously yet remain humorous in equal proportions plus all PC's are interesting, because they all exhibit some sort of insanity and are distinct from each other rather then stereotypes. The second one is Knights of the nine, I will admit it is a bit tedious to start with the whole go to unmarked shrines but hey, what can ya do, the Prophet wants what the prophet wants. It manages to give you some pretty decent equipment, a bunch of followers who while not unique are handy in a pinch (Reminder: There were very few followers introduced in Oblivion.) and you got to fight a legend, Umaril the Unfeathered.
The DLC's in Skyrim where good, the Dragonborn one was slow and hard to push through, honestly it was just more Dragons and they took the new World DLC that they introduced and just revamped Solsteim. Which was really a lazy decision on their part, they should have done something like take you to
Roscrea, it has little information and would allow Bethesda to create an entirely new lore about the area. Dawnguard, it was good, it was interesting and I could keep replaying it for fun, I loved the idea of being a Vampire Hunter and the introduction of the Crossbow was fun and their were plenty of little nick-knacks for me to go an find, so there ya go Skyrim ya got a point.
Now to the dreaded Main Quest. People went berserk over Dragons in Skyrim it was as if Christmas had been wrapped in a Bow made of Rainbows, (Though technically not Dragons by their standard they were more Akin to Wyverns.) but that was it. The dragons were easy enough to kill and the Thu'um was a cool idea that they just did not nail. The Dragonborn I want to know how he was made, their might have been information on it that I have missed but honestly, a cooler thing for them to do is give me the real power of the Dragonborn. Because the Dragonborn are Septims. All Septim were considered Dragonborn and because of that, I damn well want that power to take control of the Imperial, gather the Imperial Legion, the Stormcloaks and take the fight to the Summerset Isles. (Though I doubt I would win that war.) But I have digressed long enough. The main story line I think everyone knows by now, was dull, it was uninteresting, short (At least it wasn't too long) and felt like it was made purely so they could add Dragons to it. That is all it was, a way to get Dragons into the game. The only threat was Alduin will destroy the world. Woopty doo. When compared to Oblivion it was nothing, because Merhaneus Dagon literally wanted to combine both Nirn with his plane of Oblivion as stated by Mankar Cameron, Nirn is just another plane of Oblivion that was ruled by Lorkhan. And Dagon wanted it. Plus, added bonus, you get to travel to Oblivion! To take a war with the Daedra and murder Demons in basically Hell
Overall there is a reason that on Steam Oblivion is considered overwhelmingly positive and Skyrim is considered very positive.