Taking into account the actually release date
1. Morrowind
2. Daggerfall
3. Oblivion / Skyrim (I've put these together as I just feel that past the supposed uprated graphics Skyrim feels and plays like a tweaked Oblivion - some bits being better ( levelling) and some bits worse (The UI and less varied character progression)
4. Arena
5. Redguard
6. Battlespire
7. the mobile one
As for the comment about Main quests and Oblivion's being better than MW's - Oblivion's is possibly the worse telegraphed one in the series - totally predictable all the way and not interesting either (why most people didn't bother with it after the first play through)
The 2 things you said worse in skyrim are you nuts?! i can't say how you could possibly love oblivions UI more then Skyrims. Niether is good but Oblivion is worse than this jesus