worse entertainer or performer of all time??

Michael Bolton, Bruce Springsteen, the Dead, Kenny G, Chuck Mangione.
In classical music I would say Joshua Bell(how did he achieve that screetching he calls sound?) and among conductors it is Lorin Maazel(can't wait until his contract runs out with NYP).
There are more. Much more. But these are readily available.

Any of post-mid-1980's country music. Someone else alluded to it earlier in this thread. There's an element of hermetically sealed self containment about this sub-genre to the extent that it no longer serves as a regionally twanged commentary on life but has instead become a regionally twanged commentary on country music. Sort of like a hundred-odd high end gallery abetted visual artists exclusively painting still lifes which depict paintbrushes and tubes of oil paint. Someone must be buying lots of these five-decades-after-fact devotionals as to whether Hank would approve. Not I.

Have to agree with Priz. And what was the reason Genesis went with Phil for their singer after Gabriel left? Because his voice sounded uncannily close to Gabriel's, which you can hear on very early Genesis where Collins sings harmony with Gabriel>

Yup, Phil Collins.

The mastermind behind the cover of Supremes "You Can't Hurry Love" and the pop classic "Sussudia".

Move over Donny Osmond and David Cassidy.

This could win it all.....

Whitney Houston singing I Will Always Love You. C'mon! is there a single more anoying track anywhere? I was in London about fifteen years ago and there was a court case in the news at the time where an apartment resident had burst into his neighbors flat and smashed her cd player into 1000 bits because she played the song over and over and over all day long LOUD. She pressed charges and the judge dismissed the case on the grounds that the song could drive anyone postal!

A small measure of justice.