Best weight gainer i've seen is NLarge2. But think about this for a second, if it has 80g of carb/sugar in it why not just enjoy something that tastes much better w/ that amount of carbs? That's one thing i've never understood about people buying weight gainers, why not enjoy eating all that sugar? And then just get 40g of regular whey, and you have your gainer.
Gainers can help but you really need to stuff more food down your throat, that's what it all comes down to.
And if i have to consume X amount of maltodextrin/dextrose/sugar or whatever, I'd much rather get a piece of cake and enjoy eating all those carbs.