I think the only gambling that can be truly profitable in the long term will be smart investing. Now it depends on what investment sites or stocks you consider "smart" but if you do enough research into this kind of thing, then you can make a good profit if you keep your money in the investment for the long term to get the most profit.
I agree of this, you can not profitable in long time if you are gambler because the more you play the more chance to lose, but if you are investor in gambling company I think this is profitable and no need to gamble in a casino or what ever gambling site.