1. Bethesda (Loved the Elder scrolls series and Fallout doesn´t disappoint either )
2. Valve (Half-Life, no need to say anything more)
3. Paradox Entertainment (Europa Universalis 3, Victora II... so many good strategy games)
4. 3DO New World Entertainment (Heroes of Might and Magic 3) Yay
5. Bioware (Disregard Dragon Age II)
Honorary mention, Ensemble Studios for AoE II