The masses of the W- and Z-bosons are determined by the higgs-mechanism (see your other post), not just only their ratio. If we DIDN'T have the higgs-mechanism, we can only put their masses by hand (or just get their ratio, not both at the same time!), but now we can see that their mass is proportional to the Electroweak vacuum, hence we have a definite scale and thus definite mass-predictions (both at tree level and higher orders in perturbation theory, the results are delicate)
The Higgs mechanism also removes the divergences in gauge-boson self-couplings and in processes like e+e- -> W+W-, which makes their measured cross sections fits extremely well with theory, only in the higgs mechanism is there.
http://arxiv.org/PS_cache/hep-ph/pdf/0001/0001283v1.pdf (also full of historical refences and developments)
Including gravity is a major "lack" in all quantum theories so far, and there is no a priori reason for why gravity should be treated on equal footing as the other 3 forces at these small energy scales... the unification of gravity and the other 3 forces should happen at much higher energies, were also - quantum theory as we know it - also may break down (to e.g. String Theory). So you are mixing apples and pears when including gravity into the SM, SM has never even claimed that it can explain gravity, so one should impose that on the SM if one wants to criticize it.
As I showed you and what can be shown in e.g. the lecture notes I just gave you here, the Higgs Mechanism only has ONE missing ingredient left to be found - the Physical Higgs boson (and its mass). Otherwise, the SM is a very well tested theory and is also theoretical CONSISTENT (but not a theoretical complete description)
I agree with Humanino, you has not simply not understood the Higgs Mechanism and particle physics / Quantum Field theory yet I would say.. give it more time.. you (as many other think) thought that the only evidence for the higgs mechanism was the physical higgs boson...
Even if it is not the Higgs mechamism outlined and used in Weinberg-Salam EW theory, it must be something like that, due to the cancellation of divergences in e.g. WW production (what Humanino referred to as conservation of probability).