Creamy pudding needs slow, gentle cooking so the rice is tender and the milk is reduced.
For a luscious pudding, I prefer milk rather than cream, oddly enough. The combination of the rice starch and gently simmered milk produces a thick, rich rice pudding that belies its not-so-rich milk base. I avoid cream because it reduces and thickens before the rice cooks through—a dense, chewy pudding with a fatty mouth-feel being the result. The only exception is the Baked Brown Rice Pudding, where a combination of heavy cream and evaporated milk gives the smoothest texture (brown rice needs longer baking, which would cause the milk to break, with a curdled, watery result).
Not all rice puddings are custard based, of course, but I like the added richness of stirring in beaten egg yolks after the rice is tender. The pudding color changes from bright white to mellow yellow, while the eggs add luxurious texture and deeper flavor.