I'd say most games that need a Pentium 3 run as well on a modern computer with a few patches (even original Unreal has a DX10 renderer patch). It is really the Pentium 2 and older games that need a retro rig (Glide/DX6 "fell out of fashion" just as Pentium 3 was released).
I am kinda annoyed by people pretending low framerates is a "problem of the past through". I have a better PC than anyone I personally know, an i7 rig with 6 GB RAM and a GTX 660 that runs Metro Last Light, a famously demanding game, at an average of 50-60 fps at maximum detail with everything on full except SSAA in 1600x900 yet the first Crysis from 2007 still falls to 20 fps in every bigger firefight, sometimes even 15 fps. It doesn't even look that great, it still lags the same regardless of graphical settings, while games like Dirt 2 and 3 get me 80 fps. There are just some games that are badly programmed and optimized. I know that there are flight sims from 1994 that require a 2000 era Pentium 3 to run well in 1024x768, but what is the point? It is not like old flight sims have anything really different from the newer ones to offer (unlike about every other genre). There are a million flight sims that run well on a Pentium 2 thanks to 3D acceleration. The biggest oldschool CPU hogs were always software rendered games.
Tresspasser, well, no surprise. Fortunately, it is a shit game, so don't feel that your Pentium 2 rig is "weak", because for most old games it isn't. What I would do to have ANY retro rigs at home right now, right now I have zero 🙁 . You're a lucky man 😀 .
On topic, I'd say the Radeon 7000 is better, but a Voodoo card would be the best. It really opens a new world in vintage gaming.