This is a case of what TVtropes calls http://tvtropes.org/pmwiki/pmwiki.php/Main/GameplayAndStorySegregation, which basically amounts to that story and gameplay elements behave inconsistently.
In Oblivion the Daedra only walked around the Oblivion Gates, despite being called an invasion.
In Skyrim, the Dragons are the masters of the Thu'um, able to alter reality by just shouting at it.
Basically a single dragon simply has to use Storm Call in a city and gone is the population. But they do not use their power to the full extent. Therefore they do not seem much of a threat in game.
If Story is considered, both can be equally dangerous, since both the Daedra and Dragons are out to end Tamriel as we know it.
So, what does Skyrim suffer from?
Day-old Legend? Check (Craftable Daedric items).
Dude, Where's My Respect? Check. (Become Arch-Mage or Harbinger and people will still refer to you as "that new guy.")
Follow the Plotted Line? Check (No matter how hard you try, there is no reasonable way to avoid joining the College of Winterhold without meta-gaming knowledge)
Improbable Power Discrepency? Check (Alduin the World Eater himself has leveled stats)
Irrelevant Sidequest? Check (Balgruuf entrusts the fate of his city to you for telling him Riverwood needs an extra garrison and you saw a dragon heading to the city)
Menu Time Lockout? BIG Check (Change your clothes, down a few dozen potions, couple hundred pounds of apples, all in the space of a millisecond)
Overrated and Underleveled? Check (Final battle against Alduin is shockingly easy)
Plot Coupon that Does Something? Check (Dragonrend Shout)
Space Compression? Check (This one is easily forgivable, though)
Statistically Speaking? Check (Why can't I use that chair in a bar brawl?)
The Battle Didn't Count (Sub-Trope of Story Overwrite)? Check (First battle with Alduin)
Take Your Time? Check (Alduin will wait patiently for you to finish whatever you are doing before destroying the world)
>>Continue Your Mission, Dammit! Check (Delphine enacts a huge sense of urgency to get to Kynesgrove, but you can wait for years and the entire scene will wait patiently for you to arrive)
Took a Shortcut? Check (Delphine retrieving the Horn of Jurgen Windcaller before you despite a puzzle requiring you to Shout being present in the dungeon)
Video Game Time? Check (You can defeat Alduin, restore the Thieves Guild, perform the greatest assassination ever, and win a Civil War all before New Years)
And people wonder why this game is so unimmersive.