What computers make good gaming computers

It all depends. If you want brand name systems, go with something like Alienware. If you build your own or are considering a custom system, here are some pointers:

• Use benchmarks to help you shop for components.
• The latest of the Intel processors are great, but remember that in gaming, clock speed helps you more than the number of cores you have.
• Go with a high end video card. Those using the Nvidia Fermi are at the top. The latest Nvidia cards provide CUDA support, and that can even be used for non-GPU tasks.
• The more video RAM the better. That allows the cards to store all the textures and video data used in the game so the processor, hard drive, and bus won't have to keep loading that data.
• Multi-GPU cards are probably better than using SLI or Crossfire, but you could combine multi-GPU video cards in a multi-card arrangement.
• Get a lot of system memory and use all the channels to take advantage of channel banking.
• If you do online or networked gaming, then make sure you have decent network support. The 1 gig LAN controllers are good.
• Hard drives are another bottleneck. If price is no object, than get a SSD drive that comes on a PCIe card. If you want to use cheaper SSDs, then you should use two in RAID 0. If you use a performance array of cheaper SSD drives and you do stuff besides games, then you might want to boot from a regular hard drive (or 2 in RAID 1) and use the solid state stuff for the games in case of failure. It might do good to avoid Sandforce driven SSDs.