I started writing this in the comment section for Eric's post, but it got too long...
Look, a couple things to consider in comparing eras. Number one is that rock music was so much more mainstream in the 60s than it was today. "Stairway to Heaven" was the most requested song in history at that point. (maybe still) "Bohemian Rhapsody" was a #1 single for weeks. "Hype vs. Reality" debates concerned Bob Dylan and Donovan, both of whom are respected today. (One more than the other of course.)
When you talk about the most hyped bands of today, you have to remember that most of the country is paying attention to hip hop more than they are to rock. So maybe it would be more appropriate to talk about someone like Snoop Dogg, who had this earth-shaking debut and then got progressively worse to the point where he's now just an ironic cannabis icon.
And among the rock bands that really get the hype, I'd say nearly all of them won't live up to their billing over time. The White Stripes? Give me a break. What has that band done that Led Zeppelin or [insert bluesy punk band here] didn't do far better 30-40 years ago?
The problem with bands like the White Stripes and the Strokes is this: Led Zeppelin and the Rolling Stones were ripping off old black delta bluesmen who the vast majority of people had never heard before-- therefore, these bands' contribution to mainstream culture was a breakthrough to those with limited cultural palettes.
Contrast that to the White Stripes and the Strokes, who are ripping off not obscure bluesmen, but rather Led Zeppelin and the Rolling Stones themselves-- acts that everyone has heard and who were doing the same thing, only better, decades earlier! All these 60's/70's rip-off bands will be judged irrelevant by history because they're adding nothing new to the musical canon.
But now consider bands that really are bringing something new to the mainstream. Radiohead comes to mind for their use of electronic music and their weaving back in forth between distorted rock and hypnotic lulls. Also, Paul Simon continues to push musical boundaries to this day. (Graceland and Rhythm of the Saints were great canonical contributions, but also check out Surprise, his most recent album.)
Same thing goes for David Byrne. Other acts (i.e. Arcade Fire) might be repackaging his Talking Heads material, but not him! His solo releases continue to span in all sorts of directions. And in the spirit of both Byrne and Simon (I can't believe I'm about to say this), if Vampire Weekend were to build on their culturally off-beat debut, they, too could prove to be an important band over time. (Lots to prove obviously, but their debut is promising.)
Praising Nirvana is about as bold as buying your coffee at Starbucks, but they achieved the same thing that I'm talking about with these other bands. They took the melodic, often scream-y pseudo-punk played by their idols (Pixies, Raincoats, Wipers, etc.) and introduced it to the mainstream radio market, most of whom hadn't heard this kind of music before.
And to clarify my overall point, everyone I've mentioned has something else in common besides unearthing obscure musical genres. They were all great songwriters/performers. Kurt Cobain was a better songwriter than Black Francis, Kim Deal, etc. Jimmy Page stole his licks from Robert Johnson, but he played them in a more electrifying fashion. Paul Simon writes catchier choruses than Ladysmith Black Mambazo. David Byrne doesn't just do one genre like his influences; he does 15. So these people rose to the top for a reason.
Contrast that to the nostalgia acts that dominate rock radio (and often Pitchfork as well), and note the difference. Those bands are watered-down versions of an older, better product. Nirvana, etc. stood the test of time because they outdid their influences. That is the difference.