Shivering Isles is the only expansion Oblivion recieved, and Fallout 3 didn't get any expansions. What Fallout 3 got is DLC, Knights of the Nine, horse armor and such were DLC, Shivering Isles was an expansion, Tribunal and Bloodmoon were expansions.
When talking about real expansions, Morrowind and Oblivion were very similar so I would vote for both.
But, if we are using "expansion" to mean expansions and DLC, then I prefer the normal expansions and some DLC. I liked Bloodmoon, Tribunal, Knights of the Nine, Shivering Isles, and Mehrunes Razor.