Technically only one of my bands are officially 'split up' but they are both without their best band members (in my opinion). For me it would be The Beatles, Queen (with Freddie M) and Three days Grace (with Adam).
The Smiths, ELO have sort of disbanded, so them, and the Beach Boys I suppose. Or Queen. Most of the music I listen to is either musicals, film soundtracks, bands/artists who are still going, or single artists from the 50's/60's who are dead.
Nirvana(duuuuh) Avenged Sevenfold(I know that they haven't split up but I'd kill to see them with The Rev) MCR
I would have said FOB but they're back and I've seen them now so I'm a happy bunny
FOB's new album is great I need to go see them at some point, such a good band. As for Nirvana they would be my 4th choice, it was between them and TDG for third .