I think that sports betting gives you the most odds to win because if you know the teams and how they play and what quality are they, you van easily win. It is also the easiest kind of gambling to find a loophole in, if you know someone that knows the results ahead on the rigged game. Other games such as dice or other depend on a random generator and does not offer you much odds on winnings.
Blackjack is probably on number 2 because you need to know to play and you control part of the game. You could also count cards if you know how to.
Sport betting sure have something better chance to win but of course if you can gather good information about each game may be you can sure win but doesnt it have the same result if you bet on dice with a lower odds? The payout will be the same though and you dont even have to wait for a long time to get your result