Did you all know you can play them for free!
Link for TES1: Arena
Link for TES2: Daggerfall
You will need an application called DOSBox to help play these old DOS titles, but even in their old age they are classics
Although some would say it was Elite. That isn't open world/universe as you have to fly to areas automatically to get there, so is semi-open.
Some other older titles like Lords of Midnight etc have been claimed to be the first Open World, but again I am not convinced.
2D games are never open world due to the fact you can only go in two directions on the screen up/down and left/right, so 2 axis.
But when Morrowind was released it was wow! A Static huge world with societies and economies, and even jobs! Well there was skeletons and zombies and stuff but hey :P
3D games like Morrowind are true Open World as you have 3 axis movement.
Wonder why I posted all this >.<