Another good way to gain mass is take Protein + whole foods (fruit, peanut butter, oats especially steel cut oats, whole milk or whatever you want.You are easily able to control your macros and you will get more out of it for cheaper than pounding down weight gainer shakes.
I think if your talking about supplement wise. Probably Serious Mass is best from my personal experience followed by ISO Mass xtreme gainer after that. In all honesty though you would be better off getting oats,whole milk, banana,apple, couple tbps of peanut butter and blend it. Would equal about the same calories and protein without the dextrose from serious mass for example. However Serious Mass is more convenient and then when I add whole foods into it. It becomes unreal!
I agree, those mass gainers are garbage. Its just sugar. You can achieve the same results as throwing some pb and a scoop of ice cream into your post workout shake. I am not saying to do that , I am saying that is the equivalent.