I started waaaay back when on arena, I've still got it floating around here somewhere. I must have been around 9 or so when I played it, in retrospect that's a pretty complicated game for a 9 year old lol.
Oblivion. Remember my uncle playing Morrowind when I was a kid and then he got Oblivion. I got it late but in my opinion it was the best game of the Noughties
Started with Oblivion. The order I played in went: Oblivion, Arena, Daggerfall, Morrowind, Oblivion again because I wanted to keep things in order, Skyrim.