I don't know why people ask generalised questions like this. Nobody can tell you which strings you should get because you haven't said what you're trying to achieve. And just because one string gets alot of votes doesn't necessarily mean its the best, or the most suitable for your game.
What strings you should get depends on your racquet - particularly the weight, hoop size, stringing pattern - and what you're trying to acheive. For example, are you hitting it long and more control/less power? Do you want more spin? More longevity? Reasonable comfort? Value? Hex for example, is almost half the price of BlackCode. Is this definitely an equipment issue rather than technique issue?
Haven't played BG Ultra or Solinco Rev but of the remaning two polys, they couldn't be more different.
Hex 1.17 is great for spin, fairly powerful but dies very quickly particularly in a larger hoop / 16x19 setup. BC 1.18 is less good for spin but comparatively speaking, it lasts noticeably longer before going dead. Tornado is very mediocre. Very forgetable in all departments.
Really, you just need to set of each and try them out. It's not as if you're going to be making a decision that affects you for months and months because the playing life of polys can be measured in hours. Lots of information on the boards already about these strings.