I have lived for a current total of 42 revolutions around the sun on the dirtball, and I have asked this particular question many, many, MANY times to myself.
There have been dark times. There has been the slog of existing day-to-day, the pain of heartbreak and hopelessness, and the shame of all my personal sins that I've had to endure. There have been beatings, betrayals and other little pains that add up as time marches inexorably forward. There have been moments clouded with angry and lonely thoughts. And on multiple occasions, I have even contemplated rushing my journey into the void.
But... in the interest of being fair, I also have to contemplate the other side, as well.
There has been great joy in my life. There have been celebrations that not only would have been sorely missed if I didn't attend, but even one or two that I helped to make better. There has been applause, wonderful moments I wouldn't trade for the world, and times of quiet harmony that the world shared with me. There have been loyal friends, kind strangers and even the occasional single meetings that proved to be for the best, both for them and myself. On rare occasion, there has even been a moment or two of pure happiness.
In all, the entirety of one's existence is ultimately what one experiences... and what one feels of them.
See, anyone could look at my life and say 'boy, that poor bastard is suffering something fiercely,' while others could look at the same life and say, 'wow, what a great time he's having!' Essentially, both would be right AND wrong, because Life is not made up of black and white experiences; I've found it to consist of everything one goes through, good or ill, and is a mishmashed conglomerate of the results.
Another way to put it would be that Life isn't worth NOT living. What would it be like to have never existed? Well, that's a simple answer - NOTHING. Because not existing means never having to even think... of anything, ever.
To me, Life isn't anything that people who are in their 20's, their 40's, their 80's or even beyond truly could ever accurately define, except maybe in a scientific manner. The metaphysical part, the fun part, the hard part is so very different for each single human being that it would be somewhat silly to try to put it into direct definition or terminology. Not that it keeps folks from trying, but they have their points as well, I suppose.
To answer your original question, I think there is. I can't claim to know or define it, because all I know is what's worth it for myself; what YOU might find worthwhile isn't exactly always going to agree with MY view, and vice-versa. But I would much rather exist than not exist, and the reason I feel that way is because Life is so random. Which means that, even if all good things must come to an end someday, it also means that nothing is forever - including pain and misery.
SEEK what gives you happiness and fun, because it's out there somewhere... or maybe it's closer than you think. It's hard not to fall into that pit of existential despair, but the best rope you'll ever have to climb out with is the assurance that whatever you experience in Life is YOURS, completely and totally, and that because of that fact, you can change it as you please. You know that whole 'when you stare into the void, the void stares back' thing?
Just keep reminding yourself that, if you choose, you don't have to stare at it in the first place. Look to the horizon instead; it yields more colors and reminds us that, even as we all whirl through the cosmos on a huge ball of dirt, we get to decide for ourselves what's worth living for.