Guess, I'd like to judge only the tours, I've been following since 1992. So: The next ranking does not mean, that I'd judge the last slots as "bad tours" - they all were great and had their unique moments, but personal preferences do exist:
1. 'ZOOROPA' Tour 1993
The best show concept in Rock's history has to be #1. And apart from the stage/cabaret characters "The Fly" and the marvelous "Macphisto" there was the band playing at thier peak. from the spontaneity of the B-stage to the core of electric songs: perfect sets from first minute to the last seconds, when the stars were all, that's left. The only low point: for U2's back catalogue, you could have missed (sometimes) the changing of setlists, when you attended more shows.
1. 'VERTIGO' Tour 2005
For me of eual importance as the 1993's tour for me at the moment, having returned from the spectacular shows in East Rutherford and New York City. Musically you get U2 in their finest moments. The band is interacting all the time, you get the energy and the joy to play along with setlists, that have something for everybody: An excellent tour album with strong very tracks, being ne of the band's classic records already. Then there is the obvious "Greatest Hits" part, but with its tunes being played with conviction and punch. And then there is the resurrection of sadly liong forgotten tunes, that get tears in fans' eyes. Just listen to the BOY, OCTOBER, WAR and ACHTUNG BABY tunes or the beautiful "Runnning To Stand Still" and you know, what I mean. It will be interesting to observe, whether or how the stlists will change, when the band starts their outdoor shows in Europe next month.
3. 'ELEVATION' Tour 2001
This is the step before the current tour - and so one of the most important tours in the band's history, i guess. What I'm praising above in 2005, has been there already in 2001 - the concentration on music, playing in four and apprecating the whole musical oeuvre with a close audience: from 1980 until today. The setlists were strong, but not as revolutionary and nailed as 2005 so I have to put it back ...
4. 'ZOO TV' Tour 1992
It has been a kind of shock to see the band then - with still the 80ies images in your mind. Everything was new, fresh and confusing: the message, music, the looks and so the atmosphere of the gigs. The ACHTUNG BABY tracks were great as the chosen bunch of elder tunes - but the decision to play very static setlists and not to play any material before THE UNFORGETTABLE FIRE was something, I understand now, but surely not in 1992.
5. 'POPMART' Tour 1997
U2 at its best and worst at the same time: A great album with a special sound (So please, Bono, don't think about re-recording it - that's not necessary at all. Play them live and change them on stage, if you want to!), but a show concept, that doesn't deserve such a name. The name POP was aready not appropriate to the intimate album - as it was the trade mark POPMART. Apart from the technical brilliance of the sreen, flying lemons and martinii olives on stage, there was one huge problem: Everything drowned the essence of U2 - four people making music together! And so the - in a lot details unfinished - spectacle is something, you'll remember positive, as some single beautiful song versions, too. Next to the negative fact, that the setlists were nearly identical night after night - and never before (and hopefully never after) the music had to step back that much to optic. No, to "top ZOO TV" was a challenge, but no good idea in the end ...