Most people criticizing the Beatles seem to miss the point: describing their music (nowadays) as seeming "boring" or "nothing special" is (IMO) facile.
The Beatles are significant because of their impact on contemporary music, not just the intrinsic value of their work. Oh, and "Yesterday" remains a textbook example of a great pop song.
OT:
Each and every band from the All Time Low school of muzak. Blink-182 & Paramore don't escape this.
Green Day have been poor since "American Idiot" (inclusive).
"Loveless" by My Bloody Valentine. One of the greatest albums ever, yes. The greatest, nope.
Anything Simon Cowell is in any way involved in.
Occasional tracks aside, Oasis appear nothing special.
U2 Should have stopped after the "Joshua Tree" (which is almost as good as people say it is).
AC/DC, Motorhead, Guns and Roses. All one-song bands.
Pendulum - remove "Streamline" from their work and they're very average.
Michael Jackson - remove the presentation and there is very little to interest one.
Lady Gaga. All talk, no trousers. (occasionally literally...)
Oh, and I know that this is a "no flame" thread, but if anyone mentions Radiohead, I will destroy you.