I really enjoy playing a few hours of Oblivion every now and then.
I wasn't so keen on Morrowind because of its inferior graphics on the whole. Plus, I played Morrowind after and could never really get over the shiny pretty allure that marked Oblivion.
Morrowind might be more expansive, but the Elder Scrolls IV is already jam-packed with enough goodies to keep you busy for a long time, so who needs more?
On a side note, the way characters walk in Morrowind really niggles me.