Verified answer

1. Morrowind

2. Oblivion.

3. Skyrim

4. Daggerfall

5. Arena

1) Oblivion

2) Morrowind

3) Skyrim

4) Daggerfall

5) Arena

Skyrim then Morrowind

oblivion especially with mods

morrowind

dafferfall

and arena trailing behind

i have yet to play skyrim

Skyrim is the best sense it's the only one with a lot of DLC and extras. But I think Elder Scrolls Online will be the best one ever in the series.