Mmm.. Well, I own a G9x and I think it's at least a 4.5! Getting a gaming mouse is largely taste. I was going to get a G500 (the price IS right), but it was too skinny for my hands. So, I purchased a G9x. They're basically the same technology, but the ergonomics are different.
No Habu? No MX518?! No Lite-on Play-doh mouse??! (Ok, not really...) Come on guys.
My rankings: G9x = G500, Tact X, Sidewinder X8, Habu (Not here...), Imperator, Naga, Xai Laser, Kinzu Optical, Then the goofy little Orochi.
Mice are mainly subjective, it's hard to give ratings to mouse. Choosing a mouse depends on the buyer. A perfect example is the G9x vs G500. They're practically the same, but the G500 is too skinny and I'm willing to pay >$90 for a mouse.
The only true answer is to do your research; Go to your local electronics dealer and try out a couple mice. See if they fit in your hand nicely. Then go online, see if there are any problems with the mouse (laser engine is not good, bad tech support, etc.), and look at the specs. If everything matches up nicely, go for it!
Good Luck.