Both bands are 2 of the most popular rock acts of all time, but U2 has always been more popular than R.E.M.
In general, Led Zeppelin is more popular than U2. Yes, U2 has been probably the biggest band in the world since the 1980s; but Zeppelin still sold more records than U2 did, so Zeppelin's the answer.
ACDC
pearl jam
One band that sounds like U2 is The Smiths. Also, The Cure, The Hot House Flowers, REM, The Police, and Talking Heads are pretty similar to U2.
Never U2 sucks
u2
U2
Sunday bloody Sunday
U2 became gods in 1987, when Joshua Tree came out, but they were always a big band (at least in my humble opinion).
Some of the most popular songs from the band U2 include "One", "With or Without You", "Angel of Harlem", and "I Still Haven't Found What I'm Looking For."
U2 makes more money than Kiss, considering the fact that U2 is one of the highest-grossing touring bands in rock history.
The info is outdated but in 2010, U2 has sold more records than Aerosmith.