Pleasure cannot justify suffering in any instance -- not even in instances where the pleasure experienced greatly dwarfs the negative state of desire experienced prior. Here's why:
Think of life as a six-sided die. The five greatest things about life that you can imagine occupy five of the six sides -- perhaps intense orgasms, spiritual fulfillment, growing old with a significant other, having ten trillion dollars, and access to an endless supply of great music (these definitely wouldn't be my choices; they're just examples). The sixth side is occupied by a fifteen-year battle with AIDS -- vomiting, loss of control over bowels and all.
Would you roll the die? If not, congratulations; if presented the choice to be born or to remain in your state of nonexistence, you'd choose to remain in your state of nonexistence. In other words: You wouldn't choose life.
We don't all get AIDS, you say. Well...
1. "We" don't exist as discrete selves in the first place. I remember things that happened to a ten-year-old kid, which gives me the impression that the kid was me, but he wasn't; he lacked my ideals, conceptions, desires, hormones, and even most (if not all) of my atoms. Therefore, that ten-year-old kid is no more "me" than anyone else to have ever lived -- yet all sentient organisms utilize the same chemical compounds and electrical signals in order to experience pain and pleasure, making them chemically equivalent. Clearly, then, there is no need for "me" to experience the worst parts of life: the universe experiences them, and that's bad enough.
2. It's very probable that we will all die -- most of us from cancer, possibly while in a tremendous amount of pain for a prolonged period of time.
The worst that life has to offer might not ever get inflicted upon you, but every day, we roll the die, and every day, many, many people roll the bad side. If you wouldn't want to live through it, then how can you justify its existence?
I ask again, and hope that you leave a comment with your answer: Would you roll the die?