Thinking about it, I think Baba O'Reilly's greatness is reflected in how great LCD Soundsystem's All My Friends is become. The same weak twinkling notes, repeating in a void of empty space, sounding so claustrophic until the rest of the layers of sound kick in. The singers offering perfect lyrical reflections of their times is just the icing on the cake. The buildup from the intro is all you need to make these songs transcendent.

"U2 - Where The Streets Have No Name

From the changing time signature (6/8 to 4/4) to the orchestration and Edge's classic arpeggio crescendo, it's a two-minute journey into the world of the Joshua Tree."

It's actually all in 4/4. What happens is Edge plays a 6 note riff overtop of it (possibly creating a polyrhythm, from a certain point of view).

The band confirms 6/8 on the Classic Album series DVD, and Eno almost destroyed the studio tapes because of his frustration with it.

Doesn't matter. It's still the greatest intro in rock.