Crusader Kings II – is coming out in a week or two.  Only Christian Kingdoms are playable, and you can choose a character which is either a King, Duke or Count.

There is a live action trailer series for the game and here's the most recent one:
Crusader Kings 2 Official Sloth Comedy Trailer
very Monty Python humour.

I think in Crusader Kings II – I'll either be playing as Galich (West Ukraine) or Poland.  Although, I don't know why Kievan Rus does not exist (probably anti-Slavism if I had to guess).  Not an issue as the modding community will probably make Kievan Rus an actual Kingdom.