Daggerfall had the most skills (35), followed by Morrowind (27), and then Oblivion (21).
DFSkills = Alteration + Archery + Axe + Backstabbing + Blunt Weapon + Centaurian + Climbing + Critical Strike + Daedric + Destruction + Dodging + Dragonish + Etiquette + Giantish + Hand-to-Hand + Harpy + Illusion + Impish + Jumping + Lockpicking + Long Blade + Medical + Mercantile + Mysticism + Nymph + Orcish + Pickpocket + Restoration + Running + Short Blade + Spriggan + Stealth + Streetwise + Swimming + ThaumaturgyMWSkills = DFSkills + Alchemy - Archery + Marksman + Armorer - Backstabbing + Block - Centaurian - Climbing + Conjuration - Critical Strike - Daedric - Dodging - Dragonish + Enchant - Etiquette - Streetwise + Speechcraft - Giantish - Harpy + Heavy Armor - Impish - Jumping + Acrobatics + Light Armor - Lockpicking + Security - Medical + Medium Armor + Mysticism - Nymph - Orcish - Pickpocket - Stealth + Sneak - Running + Athletics + Spear - Spriggan - Swimming - Thaumaturgy + Unarmored OBSkills = MWSkills - Axe - Enchant - Medium Armor - Spear - Unarmored - Short Blade - Long Blade + Blade
Daggerfall must be the best game since it has more skills (i.e., content). But, actually look at the skills that were lost and gained between games. Does anyone really miss the language skills like Centaurian? Or, is anyone really bothered that Pickpocket and Stealth were merged into Sneak?
I think most of the skill mergers and removals make sense and lend the system a nice balance (i.e., 3 skills per attribute except Luck). Because of this balance, I don't think we will lose any skills without gaining an equal number in future TES games.
When not counting minor factions (e.g., the Aundae in Morrowind or the Order of the Virtuous Blood in Oblivion), DF has the most factions, followed by Morrowind, and then Oblivion.
DFFactions = Fighters Guild + Mages Guild + Thieves Guild + Dark Brotherhood + Host of the Horn + Knights of the Dragon + Knights of the Flame + Knights of the Hawk + Knights of the Owl + Knights of the Rose + Knights of the Wheel + Order of the Candle + Order of the Raven + Order of the Scarab + Akatosh Chantry + Order of Arkay + House of Dibella + School of Julianos + Temple of Kynareth + Benevolence of Mara + Temple of Stendarr + Resolution of Zenithar+ Order of the Hour+ Knights of the Circle+ Order of the Lily + Knights Mentor + Kynaran Order + Maran Knights + The Crusaders + Knights of Iron MWFactions = Blades + Fighters Guild + Mages Guild + Thieves Guild + House Hlaalu + House Redoran + House Telvanni + Imperial Cult + Imperial Legion + Morag Tong + Tribunal Temple OBFactions = Blades + Fighters Guild + Mages Guild + Thieves Guild + Dark Brotherhood + Arena
Daggerfall obviously must be the best game since it has more factions (i.e., content). However, if you have actually played all three, you know that's not true. In my opinion, Oblivion has the best faction quests when you actually compare them.
For example, compare the final quest in each Thieves Guild. The DF Thieves Guild has no final quest since all the quests are generic, the MW Thieves Guild has you killing the Fighters Guild leader, and the OB Thieves Guild has you stealing an Elder Scroll. Which quest out of these three seems most fitting to the Thieves Guild?
Overall, I prefer Morrowind to Oblivion but it's not because Oblivion has less "content". It's the type of content which is far more important than quantity. Oblivion's world was more bland and less quirky so I prefer Morrowind.
If quantity of content was the most important thing, DF would be the best TES game out of DF, MW, and OB but it's not....
You make some valid points, and I do agree overall that the quality of the quest lines in Oblivion were better than the previous TES games. If I gave you the impression that quantity was greater than quality, then I also apologize. That was not the intent. I recognized in the OP that Bethesda has made various innovations in the game play that are getting better with every TES (voice over, quest quality, combat, physics, graphics, etc). However there are also a lot of consequences to having such a controlled and focused system. Where does it end? What made TES so magical for me was that it was a fully realized and envisioned world. Morrowind in particular was really an MMO without other players (what they should be anyways). It was complex, it was expansive, it was highly customizable, and everyone could experience it and enjoy it differently. Oblivion felt a lot more controlled, a lot more empty, and overall just incomplete (it's still a great game, don't get me wrong). I'm not suggesting that Skyrim be the size of Arena or Daggerfall as that would be completely ridiculous. What I am suggesting is that Bethesda continue to do what they do, but not lose what made TES a legendary IP to begin with. This could easily be accomplished by having more developers and more funding. Which would not be an issue for Bethesda considering the success and revenue they have probably earned from Oblivion and Fallout 3 alone.