Look here.
If you compare it with previous jobs of the studios (TES series), what do we have?
1) Arena, a nice game for those times, but a bit short in comparison to the 2nd chapter.
2) Chapter 2, Daggerfall. A lot of bugs and complaints etc., but a HUGE world and a lot of free auto-generated dungeons and quests. Dungeons are sickly huge, quests are different. But after playing for a while you get used to it and get tired of the similarities caused by "random generator".
3) Morrowind. The best game for me so far (but I still love the Buggerfall, it's a game of my youth). The world is obviously smaller, but every cave and artifact are seemlessly integrated into the lore and every detail is very carefully and nicely placed, so we get an unique world with a lot of quests and things to explore. Also, the graphics gap between Daggerfall and Morrowind is HUGE so it's a great improvement too.
4) Oblivion. There were a lot of things told about it and there're wars going still between oblivion-fans and morrowind-fans, but I want to notice just 2 things. a) Graphics are definitely better but are not very different. I mean, shaders and all are nice, but Morrowind with Better bodies mod, new hi-res textures and MGE mod (allows you to view things in LOD, not the "limiting smokescreen at horison") make it very beautiful and IMO the graphics become very nice. b) The world in oblivion is more funky and seems smaller because of fast-travel and other things, although it's still quite big and there're a lot of nice quests I like. Not to mention the terrible leveled-lists system where rats level up with you and bandits wear daedric armor. Yes, there're mods, but it's not Bethesda's work.
Well, the Radiant AI is nice and it makes the game much more "alive", and I consider those bugs where guards attack each other as pros not cons because you can always think of such situation in RL, it just adds to the environment; but there're mods like Living Cities and travelling merchants and others which add scripts and schedules to Morrowind NPCs too, but as I said these are mods so Bethesda made a real improvement here.
5) Fallout. Almost no differences in graphics, quite small world and VERY limited questline. No faction progress, still the same a bit lame dialogue and other things. The main pro is the Fallout world which was not developed by Bethesda but by Black isle (RIP my friends).
So... Here comes the terrible question. What do we have for TESV? If it's gonna be a MMORPG, the series are doomed. If it becomes another oblivion with even smaller maps/questline (oblivion had a lot of quests so no complaints here) but with VATS or some other funky thing, I think that it'll be sold still but we won't have the same world again. You know, nowadays developers spend much more time to develop new graphic engines and models and animations than to develop lore, quests and gameplay factors. Sad but true.
I still hope that old fanatics dedicated enough and with skills of CS can provide us with more than just-for-1-walkthrough version of Fallout 3...