Ok, I have to ask. What is the definition of "exceptional" that this thread is working with?
Are we talking "higher stats/more advantages than NPC's" or "have an important role in the world"? My vote was based on the latter, not the former- in my games, the players are generally not some random gang of misfits brought together by chance (even though it may certainly look that way...). There's a method to the madness, built into the campaign to explain why adventures pop up around them, wherever they go. I don't tell them outright why this is so, but I will drop hints. They have free will, and can accept this destiny or not, but I do treat them as if they have an important place in the setting.
If, on the other hand, we're simply saying "yeah, they got class levels, feats, and better stats than the NPC's around them, and that's why they are special"...well, yeah, kind of.
An archmage is a CR 12 foe. He has some of the abilities of an actual PC Wizard, but he's not the same. He probably has things the PC doesn't have (resistance to spell damage) but lacks things the PC has. Now you can either just say "well, his stat block is shorthand, he's really the same as any other Wizard, the rules aren't important" or you can say "hm, there is something different about the PC Wizard".
Whichever approach works for a given group is best, naturally, but I grew up with large D&D settings chock full of named NPC's with high levels and stats, and rarely was there any explanation for why the city of Mulmaster, ruled by a 20th level Fighter, with a Fighter 16 general (one of 8), with a guild of Wizards of levels 4-12, an independent Wizard 20, a level 19 high priest, a Wiz/Priest 11/11, and so on*, can find itself in a situation where a party of adventurers levels 5-7 are suddenly vital to it's survival- unless there's something unusual about these guys (or everyone else is just incompetent, "busy with other matters" or some equally handwaved answer).
Eberron was a world where you didn't really need many high level people around to make the setting feel fleshed out, and the fact that the PC's can hit high levels ensures that one day, they will definitely stand out. I rather like this approach, because it's far more logical than trying to run adventures in a nation with a council of 36th level Wizards running things (Mystara's Glantri) and wondering exactly why there's a problem for the PC's to solve in the first place!
*statistics taken from Forgotten Realms Adventures.