Legion Hardware takes a look whether 2GB of memory is necessary nowadays:
For quite some time 512MB of memory was an ideal amount, as it kept WinXP sailing along smoothly and was sufficient for most games. However, as games evolved there was more and more data being loaded into the memory and 512MB quickly became a minimum specification. Games such as Doom 3 will not play smoothly without at least 1GB of system memory. Today most games are still more than happy with 1GB of available system memory. However, there is now a new genre of games that require even more memory. The new and very popular massively multiplayer games run best with 2GB of memory..