Rush was actually entertaining back in the Clinton days. He, just like Hannity, and Beck are just ranting "secular" preachers for the GOP. They are so predictable that there's no way Their programs are compelling radio.
What makes Laura Ingraham's show more interesting, for me is her interviews. Unlike Hannity who can't keep his mouth shut when he does have an interview, Laura let's the guest speak without constantly interrupting or talking over, if its a lib guest. Hannity is rude and talks over any lib guest which really makes it hard to listen to.
I also agree that the 35 and under crowd probably is getting the news from Drudge and probably Huffington as well other APPS, so don't need Rush/Beck/Hannity be they on AM or FM.
Also many of the 35 and under male radio audience prefer sports/talk over political/talk. Hey, I'm 61 ( I know the advertisers don't want me nor care if I listen) and there are just some days where I don't want to hear about how Obama is the anti-Christ or that Romney is an evil rich businessman, or the other stuff that seems to go on endlessly via the political talk radio format. I have and do listen to NPR, but some days I'm just not in the mood for NPR either, and find that YES, Sports/Talk is a great change of pace.
Thankfully being able to pick up most of the FM stations in Philly at work I've got two decent choices for sports talk:, 94.1 WIP-FM and 97.5 WPEN-FM, plus Fox Sport Talk on our local AM 1290 WWTX. When the Phillies have a day game, I can also listen to the game on 94.1 (our local AM Phillies affiliate I can't get at work, but the FM from Philly sure sounds great).
So part of the problem in terms of the big 3 is they now also have more competition on the radio dial too (AM and FM), not just other national political talkers including Salem's folks, but also live and local political talk shows, sports, sports talk shows, plus NPR spoken word programming (which gets good ratings at least in Northeastern Metro areas). There's just a lot more spoken word programming to choose from on the radio these days. I haven't listened to Rush/Beck/Hannity in months (Hannity its been well over a year) and frankly don't miss any of them. Listening to those guys is like listening to a music station that plays the same 100 songs over and over again, day in and day out. Laura Ingramham I listen to online at work as our local station airs her show at night IF the Phillies aren't playing.