Each player choose the way they like to play the game and this won't fit with any civ. If you don't rush in the early game, indians are better than zulu. Surely if everybody would play the same way than you could say that this civ is always better than an other one, but as each player play a different type of game some civs are better for a player even if it's not a good one for a top player.
As example, I never player zulu in MP because I don't like to rush so even if it is the best civ for some player I wouldn't be good with them. Still I can beat a zulu, arab, chinesse or roman player 90% of the time without using these particular civilisation. So I think the best civ is really relative to the type of play you like and decide to adopt and this is good because this mean that it's not everybody that play the same civs the same way in all MP's games.
As example, I never player zulu in MP because I don't like to rush so even if it is the best civ for some player I wouldn't be good with them. Still I can beat a zulu, arab, chinesse or roman player 90% of the time without using these particular civilisation. So I think the best civ is really relative to the type of play you like and decide to adopt and this is good because this mean that it's not everybody that play the same civs the same way in all MP's games.