So far my experience has shown that poker players are by far the most loyal, they seem to play most every day or at least several time a week, contributing small amounts that add up to decent amounts.
Casino players can make more money in a shorter period of time, but they don’t seem to stick around very long.
Bingo players seem to be a hybrid of the two, they make a bit of money for a short time, then come back from time-to-time to play more, but not on a consistent basis.
Sportsbetters I like the most since they bet very heavy, but they are darn hard to attract. Haven’t seen enough of them to know how loyal they are either.
My 2 cents, I’m sure the answer is the same here as it is in so many other threads…it all depends what type of site you have and how you market it.