The IROC angle is interesting. To a degree that is what has happened with the abundance of divisions/classes/sports in the shooting disciplines. You if you don't compete "up" in division (i.e. "limited 10" gun in "open" or "service rifle" in a "benchrest" match), you do compete with nominally the same equipment.
There have been attempts to run an "overall" match or championship. The games are never truely discipline neutral. Think about the Masters or something like the Sprotsman Challenge. It is doubtful you'd ever find a large enough cross over in the competitors to make a definitive statement (shotgunners shooting a Palma match).
When it comes down to it, WESHOOT2 has it correct, it's the shooter not the gear. The best shooters are still the best the order may change around in the top 20 but that's about it. Think about the times Rob Letham has put away the space guns, picked up an iron sight boom stick and smoked a major match.
That being said I enjoy shooting against people of my skill level with my class of equipment. Not that I don't watch the scores of those "above" me