its kind of a pointless discussion because no one who feels stongly about their position is likely to be pursuaded otherwise.
in the early centuries of the various groups that looked to Christ Jesus as a something to follow you had various strains of Christianity most notably the strain that won out and came to be considered orthodox and the other major strain of Christianity of the Gnostics and there were others.
Is it right for only the othodox to claim that these other groups were not Christian because they didn't believe the same things? Is it right for certain Chrisitans to essentially make the same argument today?
Anytime one tries to say that one group or religion is Christian and another is not, be they Jehovah's Witnesses or be they some mainstream religion, what they are really making a claim about is that only their definition is the correct one.
i believe that if a group claims to be Christian we should acknowledge them as christians and refrain from labellng them true or false. only Jesus can really be the judge of them.
Incidently, the basic elements of orthodox Christianity often include: baptism, the sacrament or observation of a eucharist and a trinity belief. JWs have the first two and only differ from orthodoxy on the latter. That's close enough to be considered Christian in my book.
-Eduardo