Definitely the R8500, the GF3 Ti200 is inferior in almost every respect.
3D performance, FSAA image quality, anisotropic filtering performance, TV output implementation, 2D visual quality, DVD playback capabilities, 3D feature set... etc.
The only aspects in which the GF3 Ti200 can really match up and and beat the R8500 in are FSAA performance, and anisotropic visual quality.
The Ti200 is a solid card, but with the R8500 priced similarly there is little reason to go for it.
A better comparison to the R8500 would be the GF4 Ti4200, wherein bith cards have definite and clear advantages over the other and which is better would come down to one's specific uses.
Against the Ti200 though, the R8500 is clearly preferable.