If you want a gaming machine, its better to build your own. Total control over the parts, better total value, and a lot more fun. Plus, you learn a lot about how all that stuff works. I just finished building my first one, and have lately been enduring harassment from some of the regulars here about what I have done wrong. But I won't do those things again next time, you know?
But if you're not into that, I would go with either the Compaq or the HP, since the GateWay is a P4. Gotta go with AMD for gaming. None of them are a great choice, though, unless you plan to stick a new videocard in there; integrated graphics ain't gonna cut it for a gaming rig.
Of course, if you don't care about gaming, go with the cheapest one.