You really do talk a lot of shit sometimes. Did you read that on Wikipedia? .
No, that's my personal opinion. If you can't rhyme well, or are consistently saying fewer than ~7 words between a pause (or per "line"), then you need to give up... Rap is about delivering a lot of clever rhymes in short succession while telling a story or sending a message. Random rhymes are not interesting or relate-able, slow or weak rhymes are boring as fuck. It's really quite simple.
In the example cited by Jessy Lenney above, the first six lines of the second verse are:
Spent a couple dollars on my engine
motor roaring when I back out the garage
Gin got me drunk as f-ck stumbling out the bar
Plus I'm struggling tryna find the keys to my car
Cause I be going hard, roll the camera
Life just like a movie, I'm the star
He doesn't rhyme engine and garage with anything anywhere. So basically you get to the fourth line without any rhymes. Rhyming bar, car, hard, and star is like 3rd grader stuff, and he's not even doing it with an interesting message. It's like every line or two is a completely unrelated thought. Not to mention, he has "hard" is the middle of his 5th line which basically means that the 5th line too doesn't rhyme with anything (i.e., ends with "roll the camera"). Not to mention it doesn't flow well together at all. That shit sucks, and that style of slow, childish, message-less rhyming seems to be pretty common these days; though it's especially prominent in "Southern rappers". For example, Lil' Wayne, for all his fame and success, usually sucks hard, IMHO.
Even Drake, who is getting all kinds of attention all of a sudden, isn't very good from what I've heard. His rhymes are pretty weak and slow too. It's nothing impressive.
I can't even listen to that shit. I listen primarily to Eminem and 50 Cent, and old stuff from Dr. Dre and Tupac and other affiliated rappers.
For an arbitrary "statistical" comparison, let's look at the character, word, [and "line"] counts for the song Forever by Drake (featuring Kanye West, Lil' Wayne, and Eminem; two of which are way over-hyped). This song is actually pretty good, despite only having one seriously talented rapper in it. I grabbed the lyrics from the Web and joined the lines up the way that I believe they should be joined. It's not always easy to say though so consider the line counts extra superficial. I wrote the lyrics to a file named lyrics.txt. The file contained only the verses with an artist header that looked like this: [artist name]. If you don't speak sed, tail, head, or wc: sed is used to match a single verse at a time by artist, tail is used to remove the artist name header line, head is used to trim the following artist's header line and a blank line in between verses, and wc outputs the line count, word count, and character count; respectively. Note that since there was no artist header after Eminem's verse I only trimmed one line instead of two.
$ sed -nr '/[Drake\]/,/^[/ p' lyrics.txt | tail -n +2 | head -n -2 | wc
17 150 776
$ sed -nr '/[Kanye West\]/,/^[/ p' lyrics.txt | tail -n +2 | head -n -2 | wc
22 202 1058
$ sed -nr '/[Lil Wayne\]/,/^[/ p' lyrics.txt | tail -n +2 | head -n -2 | wc
16 161 813
$ sed -nr '/[Eminem\]/,/^[/ p' lyrics.txt | tail -n +2 | head -n -1 | wc
19 223 1172
These statistics basically support the way that I would grade the complexity and skill of the verses, with one exception: Kanye West wasn't even rapping for two lines in the beginning.
$ sed -nr '/[Kanye West\]/,/^[/ p' lyrics.txt | tail -n +4 | head -n -2 | wc
20 186 980
Ah, that's a bit better. There are a few other lines that I think are ridiculous and shouldn't count, like "old money Benjamin Button, whaat, nuttin" (WTF is that?), but I'll leave those in for argument's sake.
This pretty clearly shows that Eminem has considerably more words (next runner up was Kanye West with ~37 fewer words and he even had an extra line...) and more characters than the other artists.
The word/word and character/character ratios for x / Eminem:
Kanye West: 0.834 0.836
Lil' Wayne: 0.722 0.694†
Drake: 0.673 0.662‡
† This suggests to me that not only does Wayne spit fewer words, but they're shorter/simpler words on average.
‡ Same story as Lil' Wayne; suggests to me shorter/simpler words on average.
None of these other artists even come close to Eminem, in this song or in any other song. Reading through the lyrics yourself should confirm this for you. The file that I used (which probably has a few errors in it; I didn't write the lyrics out myself) is attached. And for the record, each of these 3 insufficient rappers had relatively good verses in this song compared to their other material (even though Kanye West had a lot of ridiculous filler, he still did have a couple of clever rhymes to pull him back up with the others).