You have to answer the "should" part, but without a list of those games, no one can assure you that they will continue to work.
I don't see any reason put forth for you to change.
I do see however that the machine is barely of the right power and equipment to run XP without the owner declaring XP to be a pile of rubbish.
I have a PIII 550 Mhz 20GB 192Mb RAM AcerPower Se running on Windows 98 SE...my question is if it would be advisable to upgrade to XP, and if I do, would I still be able to keep all my programs as they are, specially my games. Please help.