tell me in terms of aggression

Well when it comes to the point that who is a better batsman among the two then for sure Ganguly is a far better batsman than Dhoni .But in captainship I would rate Dhoni higher than Ganguly.Ganguly is an aggressive captain who panics easily in tight positions of the match but Dhoni keeps his cool in  tight positions.He knows rightly that which bowler should be introduced at which position in a match and most of his experiments usually work.He changes his game according to the situation..So I would say Dhoni is a better Captain......

If he is luckier then he would have won Asia Cup recently .. .. isn't ?

I am not a cricket expert but Thoni is definitely an aggressive captain than any recent one and yes dominating too but with positive effect.