I can't actually show you, but lemme give you a few examples of how lyrical skill is relevant to the game.
1. If you take it back to the late 70's/early 80's, Busy Bee vs. KMD era, was it not about who was a better rapper lyrically? Matter of fact, if you listen to the first jab in that battle, you will hear KMD say "how many of y'all think Busy Bee (who was very lyrically basic, but a crowd mover/pleaser) can rap, rock the house? But when it comes to havin' rhymes nobody can fuck around". Then he begins to tear him down, not only by dissing him, but lyrically, with wordplay.
Take a listen.
2. Onto the 80's. Everyone's favorite group, Run-DMC, who were never as lyrical as say KMD, but still repped hard were killin' it from 82 - 86, but then your Rakim's, Kool G. Rap's, Slick Rick's, KRS's, and BDK's stepped on the scene, and kinda took the shine away from Run-DMC. Why... LYRICS. To the point that where when they released Tougher Than Leather, a follow up to their biggest album Raisin' Hell, Run definitely tried stepping it up lyrically with multi-syllabled rhymes Like Rakim.
Before Rakim.
After Rakim
3. Into the 90's. Think of all the dominant stars of this era. Nas, Notorious BIG, Ice Cube, Redman, Snoop, Wu-Tang, OutKast, Naughty By Nature, Scarface, Jay-Z, Tupac, etc. What do they all have in common? LYRICS. Think of some of the lesser known talents of the 90's. Cats who weren't mainstream, but if you were a
hip hop fan, you've definitely heard of them. Mobb Deep, MC Eiht, UGK, CNN, Black Moon, Das EFX, CL Smooth, Kam, Common, etc. What did all of these emcees have in common? LYRICS.
4. Onto the 2000's. Some of the best emcees of this era IMO, Ludacris, The Game, Lloyd Banks T.I., Eminem, Fabolous, 50 Cent (who don't be fooled by recent albums/songs, can get busy lyrically if he wants to, but knows lyrics don't always equate to sales. Want proof?
Here.
Here's further proof). All have LYRICS.
5. Now we're spoon-fed Lil Wayne (who if you listen, is not a great lyricist), Drake (who IMO has lyrically shown he's better than his boss), Gucci Mane (FOH), Soulja Boy (who uses the excuse "I'm only 16-17 so I don't need lyrics", forgetting Special Ed did his thing at that age, and Eric B. is President/My Melody was written by a 17 year old Rakim), OJ Da Juiceman (What?!?), Waka Flocka (Who?!?), Ace Hood (FOH), and a whole buncha talentless lames.