The best band Ive seen live is Nine Inch Nails. I knew nothing about them but saw them headline the second stage at glastonbury in 2000 and they blew me away! Since then they've been my favourite band hands down. No other band has done that for me.
Other very good live bands are Velvet Revolver, Muse, REM, Coldplay, Marilyn Manson, David Bowie.
Ive seen so many live bands (most of them good) its hard to list them.
Poor performaces ive seen include Incubus, Eminem, Manic Street Preachers.