I've only been once so I don't have the full experience of clubs like DC10, Sankeys etc. to cast a full and educated vote.
However, my very first night in Ibiza this summer was the Elrow opening party at Space and it was off the wall. Insanely good tunes, performers dancing through the crowd and giant buffalo costumes towering above - madness.
Amnesia we did twice and there's something special about seeing the sun come up through the windows.
Not sure I can pick yet, will report back in 7 months after my next trip!