That is also a great philosophical point- don't you still want to play those games? Should Bethesda make them redundant by taking everything, every single thing, that made them 'great' and just add a different chapter to the story?
You see, I think that's what makes the TES series so great- I can play any chapter and have a different experience due to the changes made in gameplay, stats, skills, etc. If they just carbon copied the same stats, same strengths and weaknesses and just added a 'new' adventure, I think that would get old fast. Isn't that what we complain about the shooter franchises? "Oh, Call of Duty 3 is just the same shooting game but with different missions."
They might as well add them. It's not like we're getting a bunch of new stuff with Skyrim. Smithing (linear crafting mechanic), a handful of perks that actually add something new to the series, shouts (title specific mechanic) and dual wielding weapons. That's about it. If your not going to put the staples of the series in, you at least have to replace them with enough stuff. They didnt. Sky would be a better game with SC, acrobatics, H2H skill, degradation, inherent variables, etc. Then you wouldn't have to go back to the other games as much, and for simple things like creating a spell, jumping high, running fast, climbing, flying, using spells that are no longer in the series, etc. The/Your "difference" is just having less. Yes, 5 is different from 4, because 4 is less.