BruceVC
Magister
I left the question broad, part because I wanted the essential list, partly because I haven't played many rpgs. I sank a lot of hours in Skyrim when I was still playing games, but now that I have the leisure time, I want to play the essential rpgs. Then figure out which I like and play the derivatives.
If you loved Skyrim you must play Oblivion, Morrowind and Daggerfall and of course make sure they heavily modded. We have some relevant threads on these games and suggested mods