Over the last 2 drafts the here's how the draft breaks out:

• 98+ recruit rating: 7.95% of draftees
• 96-98 recruit rating: 7.75%
• 94-96 recruit rating: 4.84%
• 92-94 recruit rating: 5.23%
• 90-92 recruit rating: 5.81%
• 88-90 recruit rating: 12.60%
• 86-88 recruit rating: 13.76%
• 84-86 recruit rating: 13.57%
• 82-84 recruit rating: 9.11%
• 80-82 recruit rating: 3.10%
• 78-80 recruit rating: 2.13%
• Sub 78, but rated: 3.68%
• Unrated: 10.47%

So that makes it look like ratings aren't that important, that most NFL draft picks come from the 84-90 rated range.  But it doesn't account for how often each rating is given.  There's a LOT more 85 rated players than 99 rated players, so what we really want to know is how much more likely a 99 rated guy is to be drafted than an 85.  

For this, we're only looking at players that are rated.  A fair number of unrated players do get drafted, but we need a defined sample size, and the number of recruits who aren't rated is near infinite. 

So we will just look at the likelihood of a given rated recruit being drafted, as compared to the likelihood of a random rated recruit.

• 98+ recruit rating: 8.52x more likely to be drafted than the nominal rated recruit
• 96-98 recruit rating: 6.96x
• 94-96 recruit rating: 5.33x
• 92-94 recruit rating: 2.95x
• 90-92 recruit rating: 2.30x
• 88-90 recruit rating: 2.65x
• 86-88 recruit rating: 1.51x
• 84-86 recruit rating: 0.96x
• 82-84 recruit rating: 0.59x
• 80-82 recruit rating: 0.18x
• 78-80 recruit rating: 0.17x
• Sub 78, but rated: 0.41x

So if you're wondering how much more likely a 98+ recruit is to eventually be drafted than a 78-80 rated recruit, it's 8.52/0.17 or 50.72x more likely.  An 88-90 is 1.75x more likely to be drafted than a 86-88

Unsurprisingly higher ratings are even more important in hoping to be drafted early.  Among 1st round draft picks, the ratios become

• 98+ recruit rating: 28.81x more likely to be 1st round drafted than the nominal rated recruit
• 96-98 recruit rating: 10.71x
• 94-96 recruit rating: 9.84x
• 92-94 recruit rating: 2.52x
• 90-92 recruit rating: 2.36x
• 88-90 recruit rating: 1.57x
• 86-88 recruit rating: 1.48x
• 84-86 recruit rating: 0.32x
• 82-84 recruit rating: 0.29x
• 80-82 recruit rating: 0.09x
• 78-80 recruit rating: 0x
• Sub 78, but rated: 0x

And if we expand it to the first 3 rounds it comes out to

• 98+ recruit rating: 15.39x more likely to be drafted in the first 3 rounds than the nominal rated recruit
• 96-98 recruit rating: 10.21x
• 94-96 recruit rating: 7.61x
• 92-94 recruit rating: 3.63x
• 90-92 recruit rating: 2.35x
• 88-90 recruit rating: 3.02x
• 86-88 recruit rating: 1.58x
• 84-86 recruit rating: 0.49x
• 82-84 recruit rating: 0.42x
• 80-82 recruit rating: 0.09x
• 78-80 recruit rating: 0.08x
• Sub 78, but rated: 0.17x