We have three boys from the same breeder, an F3, F4 and F5. Our F5 boy is extremely social, to the point of begging to meet new people (we actually went to Petco to play last week and he made friends with 15 people- FIFTEEN).
Our F4 boy is shy at first, but extremely cuddly with Michael and me, and friendly with anyone who is in the house for more than about 5 hours.
On the other end of the spectrum is our F3 boy, Jarvis. He was described by the breeder as kooky and goofy. We bought him to be our F5 boy's friend, because it turns out I am highly allergic to housecats (but strangely not savannah's), and our rescue from the shelter needed to move out (I have reactive airway syndrome, and could not keep her, but thankfully my first kitty love, LeeLoo is happy in her new home). Jarvis arrived very young (8 weeks), and we, NOT the breeder, still had a lot to learn and did not do a great job socializing him. Today, Jarvis is a happy, healthy boy who enjoys being around us. He will never come up to a stranger and beg for attention, but he is happy to be around us, he sleeps in bed with us, follows us around the house, loves play time, and is a happy cat. Is he outgoing? No. Is he social with strangers? Nope. Is he a happy, healthy, wonderful member of or family that we adore? Yup. And if you adopt a kitten that is a bit goofy or kooky or shy, like we did, keep in mind that he will love you just as much as that outgoing kitten will- he just might express it in different ways, and that is just fine.