The main thing that can be a problem with any type of game is the graphics, as the server is just recieving key and mouse infomation from the client and sending screen refreshes back, any "animated" application (strongly recommend that you turn off that infernal paperclip help tool in office, and NEVER use screen savers on the Terminal server...) can cause network and processor load.
you dont want to attempt to publish anything that requires anymore than 256 colours if your intend to do this on any server less than an absolute monster. So you will need to ask if the requirement will justify the costs required in purchasing such a server(s)...
Your best bet is to hope for a reply from Citrixenginner however, as I know he has had experience of this, If I remember correctly he managed to get Quake running... hehe, now if that isnt graphically intensive, then I dont know what is...
Games also generally use sound to compliment the overall "user experience" that makes them enjoyable... this will also put considerable pressure on your network and servers.
This could be a costly exercise and may not be the best "priced" solution...
Any more details on the software/number of users would help in giving a better idea of your server requirements.
Hope this helps...
Steve Marshall
Group IT
Technical Support Supervisor
(aka General Meddler)
The Expro Group
Reading
UK