Okay, Whole Lotta Love is pretty easy.
Hmmmmm..........don't know about that one. I've been slinging a rock 'n' roll axe for well over 30 years (and considered pretty good at it).....and I find "The Immigrant Song" VERY difficult to play properly. There are no fewer than 5 individual notes (ok, 2 notes: one played four times, the other played once.....an octave up) played in that riff, and damned fast. Every guitarist I've seen try to play it with the wave of a hand blows it. They truncate the riff.
Speaking of riffs.............can anyone name another guitarist who is better known specifically for his riffs than Jimmy Page? I mean, I believe that there are plenty of guitarists who can mop the floor with Page (Gary Moore, Frank Marino, Eddie Van Halen, Nuno Bettencourt, etc.), but with the possible exception of the inimitable Brian May of Queen, no one else has plied the airwaves with so many readily-recognizeable, hooky riffs as Jimmy Page.