I recall an interview on Tech TV (a few years ago), where they asked a PC "game" developer if there was any sort of an agreement among the various companies as to the backwards-compatibility of new titles. His response was something to the effect of:
"No, not officially, but off the record, we all more or less agree that a three year-old system is about as old a set up as we'd want to support".
Flight sims that where released in the 1997-1998 period would NOT run well on anything older than a 2-3 year old system (though in all fairness, Pentium processors were only released at the end of 1993, and 3D graphics cards were quite uncommon prior to 1996).
By late 1999 early 2000, most titles coming out were written with hi-end PIIs and PIII's in mind. For example, Jane's USAF (released at the end of '99) was coded to take advantage of the PIII's SSE capability. And the PIII was only 10 months old at the time...
In closing, remember that SFP:1 was written in 2001-2002, and was officially released in November of 2002. I personally know at least two members of this board who are running it on PIII systems, even with the latest patch installed.