PCSX2
The PCSX2 is widely regarded as the best PlayStation 2 emulator, emulating the console's code so you can put a PlayStation 2 game in your computer DVD-ROM drive to play it. The minimum system requirements are a Windows XP/Vista or Linux 32 bit/64 bit operating system with a Pentium 4 processor and 512MB of RAM. Recommended requirements include a Windows XP/Vista or Linux 32 bit/64 bit operating system with a Core 2 Duo 3.2 Ghz processor, an Nvidia GeForce 8600 GT graphics card or better and 2GB of RAM.
NeutrinoSX2
The NeutrinoSX2 is an open-source PlayStation 2 emulator that is constantly being updated and modified and is capable of playing PlayStation 2 ROMs. The recommended system requirements are a Windows XP/Vista operating system with an Intel Pentium 4 2.0Ghz processor or better, 512MB of RAM with 5MB of free hard drive space for the application and 200MB of free hard drive space for various ROMs, Microsoft DirectX 9 for graphics rendering and a powerful video card like the Nvidia GeFroce 8600 GT.
Emution
The Emution is a relatively new emulator that is known to play only a few demos and no commercial games as of 2010. According to VTEmultion, the recommended system requirements are a computer with at least 2GB of RAM, a Dual or Quad Core processor, and a high-end graphics card such as the Nvidia GeForce 8600 GT.