nah they're the best because they have a shitload more units types that fill every role so far found in SC2.

seriously, they have unbelieveably good harrassment, cheap incredible pillars of their army that compliment every other unit they have (the marine), they are extremely cost effective, and have the biggest defenders advantage in the game which allows them to come back and win AFTER they fuck up incredibly bad.

not to mention the best macro mechanic which is enhanced by gold base's, and a tech line where 90% of all their unit's are on their main techline (everything except ghost's and BC's) AND they can change army compositions and openings any time they want.

Thats why it's the best.
terran just have so many incredible options, where as if your a zerg and you build a roach warren, it doesnt magically become a hydra den by moving the building 3 paces to the left.

Zergs have agility and map control and lategame vision.

Protoss have cost effciency and the biggest attackign advantage in the game (warp gates)


but neither has anything CLOSE to the amount of options terrans have.