not true. i'm pretty sure that no grandmaster today can beat the worlds top chess computers. kasparov lost or drew the last few matches he played, he definitely did not win. there's just no way. when you have a database of all the possible branches and variations and know the best move for every possible situation, you just can't lose. this is because chess is "limited" in complexity in that it only has 64 total squares and only so many legal moves. the computer does not think, it just does a search for the best move based on some algorithm that i should know if i had taken a course in AI (alas I didnt).
civ however, is far more complex as you say, as there are far more possible actions, and far more tiles.