Blackjack, Poker, slots, roulette, baccarat, sports betting, horse racing, betting on sociopolitical events, keno, etc.
I will go with blackjack, not a fan of it but you need to be smart and step up your game to be able to come out hole but as for sport, you need skills and you need to know your ways in analyzing but not too deep analysis, you need the basics to win sports games. If intelligence is a measure on how gambling is won, I don't think even an illiterate will win but I have street hawkers, Bikemen and other people that does all type of sophisticated odd job and they win big amount of money through sport betting.
However, each of them has need intelligence to survive particularly when it comes to things like managing Bankroll. You can roll a dice a single time with a big amount of multiplier and recover the money you have lost for the whole weeks, even in sports betting but if you are not intelligent on when to walk out and call it the day, the casino forces will take all from you and would have to go back to genesis, this is where I think intelligent is necessary in all types of gambling.