R.E.M.'s influence has been as widespread as any rock band's of the last 30 years, though I don't think it's necessarily always discernible. They didn't invent jangle-pop (or however you want to classify it) but they certainly popularized it, and there have been hundreds of bands who have co-opted the style from them since. This is still going on in today's indie-rock scene--Real Estate's self-titled and
Days albums are two examples, off the top of my head. Hell, I liked The Decemberists'
The King is Dead largely
because it sounded like R.E.M. (at times, that is), which according to Colin Meloy--and considering Peter Buck guests on the record--isn't a coincidence. And Stephen Malkmus dedicated an entire song to how the band has impacted him (
http://www.youtube.com/watch?v=0DvVYwXqFEE).
Their influence in populist circles has been just as vast. Groups like Counting Crows, U2, Coldplay, Nirvana, and, yes, Pearl Jam have cited the band's effect on them. Again, you couldn't necessarily deduce this from the music these bands make, at least not all of the time, but I think that largely has to do with how difficult it is to create a genuine facsimile of the R.E.M. sound. Regardless of which era of their career you're talking about, nobody has ever nor will ever sound like R.E.M. beyond a superficial resemblance, just as nobody will ever sound like the Beatles beyond a superficial resemblance, and in my mind that's far more indicative of greatness than selling 95 million albums or the fact that Eddie Van Halen is your guitarist.