My Final 4 would be -
North - Blizzard (a romp. PopCap and Naughty Dog have a great match in the Sweet 16, but no match for power of Diablo in the Elite 8)
East - Bioware (LucasArts falls in the Sweet 16 and then BioWare narrowly defeats Firaxis. UbiMontreal was also in the running)
West - Epic Games (Nintendo gets upset in the Sweet 16, and the bottom of the bracket is weak)
South - Valve, but this is the stacked division. Crytek is a great 8 seed, and Rock Star San Diego comes from the bottom half. Valve crushes all comers though
Blizzard vs Epic
Epic came from a weak group, Blizzard crushes them in a one sided matchup
Valve vs Bioware
Probably my two favorite developers. Portal, HL2, CS:S, TF2/TFC beat KOTOR, ME, Dragon Age, but it's close. Valve tosses in a buzzer beating modification (Gary's) and takes it
FINAL!
Blizzard vs Valve
If Diablo 3 had come out now, it might be Blizzard. Unfortunately for them, I'm not a WoW guy and I haven't played much of SC2. Valve's portfolio gets them the win and they get to pull out the motherboard!