Yeasayer
Before: Strange world music-influenced eclecticism
After: Identikit Brooklyn “hey, look, we have synths!” stuff

Depeche Mode
Before: Slap-happy, mildly camp synthpop
After: Portentous stadium rock

Pink Floyd
Before: Winsome psychedelic noodlings
After: Portentous stadium rock

The Horrors
Before: Misfits cover band
After: Shoegaze devotees

Radiohead
Before: Best guitar band of the ’90s
After: Warp devotees

M83
Before: Freeform pysch extravaganzas and ambient excursions
After: Pitchfork pop

The Clash
Before: Angry left-wing punks
After: Angry left-wing musical visionaries

Best Coast
Before: Most excellent psych weirdness
After: Sub-girl group Cali tedium

Robyn
Before: Cheesy pop and child stardom
After: Hyper-cool electropop and angular haircuts

Nick Cave
Before: The Devil incarnate
After: Suit-wearing piano balladeer

Who I like both “before” and “after”: Nick Cave, Radiohead and The Clash.

Who I like “after”: Depeche Mode and Pink Floyd (does that make me portentous?)

Should probably check the others out some time.

Obvious (big name) omissions include: The Beatles, U2, Neil Young, Pearl Jam, Sting/The Police.