What we call pleasure is effectively the way that we have evolved brains that learn to do what promotes survival and reproduction. Animals get pleasure when we do things that contribute to our survival and reproduction, like eating certain foods or mating; this makes animals (including humans) tend to repeat the behaviors that led to those rewards (of course, just because something is pleasurable doesn't mean it evolved to be that way for the same reasons as other attributes).
We already have ways to "create" pleasure: to do so, you activate the brain receptors artificially that normally are used to inform the rest of the brain that you just did something "good": heroin works great. So do amphetamines, cocaine, MDMA, etc: drugs of abuse. That's why they are drugs of abuse: they hijack the brain's reward system to make taking the drug pleasurable and therefore encourage future behavior to achieve that pleasure.
In animal models, we can also be more direct and use electrical stimulation in the brain to do the same thing: stimulate in the medial forebrain bundle and animals will learn to do whatever led to the stimulation (German & Bowden 1974), even to the point that the reward is saturated (Waraczynski et al 1987) and to the exclusion of other normally pleasurable activities: for example, water-deprived rats will lever-press instead of drinking water (Morgan & Mogenson 1966).
There might be usefulness of these approaches in treating certain types of depression, but otherwise "endless pleasure" seems to not be all that pleasurable due to adaptation and because pleasurable stimulation is relative.
We can already artificially stimulate the areas of the brain involved in "pleasure"; the result is not great in the long term.
German, D. C., & Bowden, D. M. (1974). Catecholamine systems as the neural substrate for intracranial self-stimulation: A hypothesis. Brain research, 73(3), 381-419.
Morgan, C. W., & Mogenson, G. J. (1966). Preference of water-deprived rats for stimulation of the lateral hypothalamus rather than water. Psychonomic Science, 6(7), 337-338.
Waraczynski, M., Stellar, J. R., & Gallistel, C. R. (1987). Reward saturation in medial forebrain bundle self-stimulation. Physiology & behavior, 41(6), 585-593.