Well, i guess you CAN do the game quick if you wish. Beths own Dev Team speed run challenge took their best guy just over two hours for the MQ alone - But thats just done for a giggle and their in house trophy.
Looking at it the other way around. Skyrim has more content than Oblivion and I have well over 1000 hours on Oblivion !
Other thoughts - i bet you fast travelled all over the map, didn't you? c'mon admit it - how much did you take the time to really explore, on foot, like you really would have to. Fast travel is cheating (ha! can of worms! flame suit on) - walk it all (ok jog if you like) get into all those random fights and discoveries - if you can't be bothered, your not playing the game, just blitzing it.
Need more challenge????? Play like its for real. Like your really there (nah! don't dress up to play, ha!) i mean, in real life if a bear eats you - your dead - totally, thats it. Theres no re-set button in real life - so try the game playing 'dead is dead' if your character gets killed at any point you re-start from the very begining. Its a tough challenge, but belive me it gets the adrenaline pumping when you face off a bad ass creature and you've put 100+ hours of blood sweat and tears into that one character and can't afford to let them simply die. It really does make encounters exciting and scary - like for real..........
I'm not doing a Dead Is Dead walkthrough on my first run, maybe in the future, but I'd be insane to do it on my first character. Also, I only fast traveled later in the game. I did spend the first 20-30 on foot just exploring, but face it, eventually you start to run into the same place over and over again, and I don't consider that really exploring, or even new content. For example, if a companion quest has me travel to rorikstead and back, I might walk there, but I'd fast travel on the way back because it is just the same journey in reverse. But believe me, I have done quite a bit of exploring on my character