I often play dice, it's simple and entertaining. I have been using this website for many years: primedice.com, it is probably the most popular in dice sites.
Dice is indeed popular and back in the starting days of primedice and its predecessors back in 2013 it was the most popular game. As time passed more development in tech happened and more games were developed to replicate the real casino games. Slots is what gamblers drool over, if you ever visit the Vegas strip you will understand. It is similar here too, these are easy to play games and are often the maximum spending site for gamblers.
But for a subjective statistic, one must run a survey.