Anybody wonder where is 72 virgins term coming from?

Wow, isn't it that too good to be true? I would pity those 80,000 servants and 72 virgins. If one person can have this much, then heaven must be full of slaves. That way, i would prefer being a slave in heaven rather than suffer in hell. but wait, why should i long to be one of the slaves or servant if there is a way I can be among those having servants and virgins of my own? BUT THIS ONLY SHOWS THAT ISLAM IS NOT LOGICAL. Where do you think would the 80,000 servants and 72 virgins would come from? Aren't all people created equals?