"suck"="be very unsatisfying"

     [This is a fast-access FAQ excerpt.]
It is pretty clear that "suck" started out as a sexual insult,
e.g., "Charlie sucks", what he sucks being unnecessary to spell out.
As a term of general disapproval it did not take long to be applied
to all sorts of things, animate and inanimate, to the point where it
is now used by all manner of people, small children included,
without any consciousness whatsoever of the sexual origin of the
term.  Some of them seem to find it very hard to accept that it ever
had a sexual connotation.  It has crossed the Atlantic, but would be
regarded both by those who use it and those accustomed to hearing it
as a conscious Americanism.
   The curious thing is that "sucks!" as a taunt or term of derision
seems to be even older in U.K. english, but it has never to my
knowledge had any hint of a sexual meaning attached to it, though
that doesn't mean it never did have.  The construction is not at all
the same as the contemporary US phrase.  To quote Eric Partridge's
Dictionary of slang and Unconventional English:  "Sucks!  An
expression of derision:  schools (?mostly boys') since late C19.
Often sucks to you.  E. F.  Benson, David of Kings (1924) has
Sucks for----!  (That's a disappointment for so-and-so).  'Sucks to'
may also be directed at others, e.g. 'Well, sucks to them! they can
jolly well go without'."
   But for people of a certain age, "Yah boo, sucks to you" is
indelibly associated with Billy Bunter, a fat schoolboy created by
Frank Richards (1875-1961), and immortalized in children's books and
comics of the period.  Even when I was a small boy in the 1940s,
"sucks" in that context sounded old-fashioned and upper-class, and
personally I've never heard or seen it except as a conscious parody
of Bunter.