Rush Limbaugh is the most influential talk radio host in America and has been for the past thirty plus years. It's thanks to Rush Limbaugh that right wing or Conservative ideas and talking points were able to reach millions of Americans, especially as Cable News grew and there was a gradual but steady leftward drift in almost all other mainstream news outlets including both Cable TV News and stuff like newspapers and magazines. Back in the time before the Internet and even the rise of Cable News networks it was Rush Limbaugh who was the premier Republican voice especially during the 90's.
The fact that Fox News and the Drudge Report on Cable TV and the internet respectively became so popular is very much likely due to the absolute
dearth of actual Conservative or right leaning mainstream media beyond talk radio. I personally never listened to Rush Limbaugh but I have heard other nationally syndicated political talk radio hosts and folks like Dennis Prager (who founded PragerU), Sean Hannity, Laura Ingraham and others got their starts on talk radio. So his influence is felt even well beyond his direct influence. Rush Limbaugh and Conservative Talk Radio were such an annoyance to Liberals that they tried to use their government power to create things like a
"fairness doctrine" (affirmative action for liberal opinions) for talk radio and launched largely failed efforts like Air America as rivals to Conservative Talk Radio. He was probably crucial for the Republican takeback of Congress in 1994 as well.
Eventually Fox News and later the internet and plethora of new media options came out, but millions of people still listen to Talk Radio and honestly the only Conservative figure who might've come close to the influence of Rush Limbaugh in this era was likely that Bill O'Reilly guy who helped make Fox News the juge media juggernaut it is today.