My first TES game was Morrowind... god... it left me with an Awe O.O feeling. Everything I had ever hoped for in a pc game (yeah, I played it on the pc)
My second one was Oblivion, though I started playing it late due to the lack of hardware... at least I played it and finished EVERYTHING in it

My third game was Daggerfall because everyone kept saying how large it was that it was great and stuff... so I played it cause of you guys. Thanks

Considering plot, originality, feeling and the ability to keep me playing it for months over months, Morrowind is the first place winner here.
Afterwards comes Oblivion, which was a great game, but failed me in certain places (mainly with the plot and the final boss).
Then comes Daggerfall, which wins the complexity and the ability to drive you insane in certain parts award.

That's my opinion

nice thread btw.