REM's a good call - I don't get why they're so popular either. I'm a huge fan, and I think their music is mostly brilliant (still not convinced about Reveal, and Up is very hit-and-miss) but it took me many years of gentle immersion to get to the point where I really like them, and most of their albums take me several years to get to like. They strike me as being rather "difficult" and inaccessible - not the stuff of "biggest band in the world" as I've seen them called.
Of course, they come out with the occasional pop superhit ('Losing My Religion', 'Everybody Hurts'), but somebody out there other than myself and the other diehard REM fans must buy whole albums or they'd never be as popular as they are. Shrug.
Having said all that, I suggest anyone who doesn't "get" REM have a listen to their first two albums, Murmur and Reckoning, from way back in 1983 and '84 (?). Simple, energetic, wonderful fun.
Dunc