I gotta partially agree and disagree.
You see, while you can't really say a genre is bad, when you look at music from a technical level, you can say individual songs and artists are bad, at least relative to their contemporaries in terms of the expectations of the genre(s), overall musical expectations, and originality.
Yes, so some music is just bad.
That said, it's pretty hard to tell really unless you're schooled in music theory so random youtube idiots generally are like "my personal opinion is better then yours!1!1!"
As for Lil Wayne, he's a troll, his music is good for dancing to and generally funny to listen to but his solo stuff should be taken like that, as trolling.
When he works with other artists though, he can do some great serious stuff (like My Life).