Anytime anyone goes out of their way to indicate that they are not a racist, you can safely bet that they are about to say something racist. I'm glad to see that OP has not broken that rule.
Seriously, first off, I like Boondocks too, but let's not go confusing it for a comprehensive summary of the issues. If that's where you're drawing most of your knowledge from, and it seems to me that that is the case, then you might not to want to go trying to make arguments like this. That is to say that before you go saying something, maybe you should actually learn about it first.
Second, you'll find amongst any group of people, regardless of race, that there are probably more famous entertainers and athletes than any other sort of famous person. I mean, seriously, if you were to ask any random person on the street how many actors and actresses they could name, and then how many politicians they could name, you'd get the names of more actors and actresses from the vast majority of the people you talked to. But when you're talking about African Americans you've got a smaller sample size to start with, so if the sake of argument, the average person could name ten actors/actresses and five politicians, and the overall black population makes up about ten percent of the overall demographic, then one of those actors and one half of those politicians would theoretically be black. But even a basic sociology course would reveal to you why the average person would probably be able to recognize even fewer famous black people than that. And, yes, even after that, there is a smaller percentage of black people working high profile jobs, because on the whole the African American population is statistically poorer, and high profile jobs take money to get to in the first place.
Then let's address the rap issue. So yes, there is a sizable portion of rap that is pretty much meaningless commercial garbage, and in the case of rap a large portion of the commercial garbage part of rap is the "gangsta" rap stuff. But look in ANY musical genre, and you'll find that a large portion of it is mostly commercial garbage. There is plenty of rap out there that does choose to look into deeper issues, so give it a chance before you go dismissing an entire genre.
And as for your final question, you've made it almost impossible to answer to start with. Higher intelligence almost always correlates positively with age. I can't think of any famously intelligent white people under the age of thirty five either. Our philosophers, politicians, scientists, and all the other men and women we respect, they're almost always over thirty five. And as I mentioned before, since the portion of the population that is black is a minority, there will be less people to start with. But take away your ridiculous "under thirty five" bit, and you'd find lots of people who qualify. Just to name some names off the top of my head, our president, whether you like him or not, there's no denying that Barack Obama is an intelligent man. Neil Degrasse Tyson is incredibly smart. Spike Lee is a brilliant film maker whose movies have depth and meaning, regardless of whether you agree with their meanings or not. No one else occurs to me right now, but like I said, that list is just off the top of my head.
Let me say one other thing as well, have you ever considered that the media purposely chooses to avoid creating intelligent black characters? The unfortunate fact of our society is that we actually like to laugh at black stereotypes, and the media we create reflects this. There's an excellent Spike Lee movie called Bamboozled that really gets to the heart of the issue, if you've seen Network before, it reminds me of Network but with an afrocentric theme twist. Still, just take the time to consider that maybe you've simply been fed media to imply to you that what you said is the case, and remember that like all media, what is presented to you may very well not be reflective of the truth.