He is right, it really depends on if you have AGP or PCI-E.
There also might be some other things you can also do to improve performance, I would upgrade to 1GB of ram if you do not already have it.
Good PCIe card, and extremely low price for the performance you get:
Newegg.com - EVGA 256-P2-N624-AR GeForce 7900GS 256MB 256-bit GDDR3 PCI Express x16 KO Video Card - Retail
AGP is bound to be more expensive because it is going towards the direction of being obsolete. However, this card should give you good performance:
Newegg.com - EVGA 256-A8-N542-T2 GeForce 7600GS 256MB 128-bit GDDR2 AGP 4X/8X Video Card - Retail
If all you have is PCI, your performance will be low no matter what and I would strongly recommend a new computer with up to date graphics interface, however if you want to stick with PCI, I would go with :
Newegg.com - JATON VIDEO-338PCI-DVI GeForce 6200 256MB 128-bit DDR PCI Video Card with L-P Bracket - Retail
Of course, there are many other options, those are just the few that I recommend, there are other lower budget options as well, but those top two cards will allow you to play a wide variety of games beyond Sims 2.