I love TI 3rd edition, but can't always get together 3 players willing to commit the amount of time it takes to play a game.
Are there any 2 player variants of this game?
There is no official 2-player variant; the game just wasn't designed for it.
But as always, the internet provides. Various fans have proposed two-player rule sets.
The Roland Wood variant is probably the most commonly used, building on earlier suggestions by other players.
(There was another popular version in the "Shattered Expansion", but I can no longer find a live link.)