I say Zerg is really strong if you can mass produce them but on general they are weak if outstrengthened.
Terran is awesome on the Siege Tank defence. It was a really wall. Bunkers--> layer 1. Missle Turrets--> layer 2. Siege Tanks--> Layer 3. If that's not enough then put Gorillas as backup. Then again. A lot of resources is needed for this one. Really Strong but then needs a lot of resources for a good offense and defence.
Protoss. My favorite among all the 3 of the factions. Well balanced. Although they are energy crystal eaters, they are pretty good. I like the efficiency of their towers. Can attack both land and air

Dark Templars pawn too. Then again... Must use them wisely or else wasted >.>
They took out the Interceptor of the Protoss so I kinda feel sad for that. That unit was like my initiator for barging into the enemy base.
For SC2 I think the Terrans are over powered but still. Weaken them at early game with a zurg. Total pwn. Zerg can easily reroduce at early so no worries on your army of roaches
