If you look at the south Korean grandmasters it's dominated by Terran in Win/Loss statistics, and blizzard themselves recognise this, however this is probably due to the popularity of rush tactics in Korea, which Terran is the most versatile at of the 3 races.
And oric, you just supported what Joe has said, Terran is easy to learn, giving people who play Terran off the bat an advantage over people who choose another race.