I think we're only scratching the surface here. As Art says, Shupe's a/c are magnificent - payware dev's won't touch his type of a/c for obvious reasons, no money in it.
Then we have Lionheart who works on the same principle: Make quality products but choose 'rare' a/c which the big dev teams won't touch... except he charges money for his work and gives it all to his church.
So here we have two one-man dev's (who sometimes do get a little bit help from their friends), both of whom produce quality... one freeware, the other payware.
And then there are the other freeware one-man dev's, Dino and Piglet as bel mentioned, Mike Stone in the past and Piglet must be the most prolific of them all, on the other side of the coin again, Dino Cattaneo less prolific but work of the highest quality. Running the risk of repeating myself, D.C.'s F-14 for FSX stands head and shoulder above the rest... well, what do we have, the Iris comes to mind and I think there might be another or two payware F-14s out there.
I also have a strong feeling that no payware teams will make another F-14 for FSX, nor will they make any carriers considering that the Nimitz and the Clemenceau are freeware and the high quality of these carriers.
Back to FS9, Olson's F-16 and all his other a/c are free and there are no better ones out there, the same goes for the F-18 by the Japanese FS KBT team. Oh yes, the 'Superbug' F-18 (payware) was announced and I got all excited... it's back in the hangar collecting dust. When I wanna fly an F-18 in FS9, I use the above mentioned freeware product.
Now let's look at helicopters. The Nemeth Brothers have always made high quality choppers for FS9 and now for FSX - payware but the quality and detail could be compared to PMDG and the Level D 767 in the airliner department.
The hit-parade of choppers would be covered by payware Alphasim (now Virtavia). I certainly do not want to belittle Alpha... for their enthusiasm and what seems like an endless stream of 'yet another model' alone, they deserve 5 stars, plus so many of their helicopters (and other a/c) where never made by anyone else.
BUT... compare the Alpha payware Blackhawk with the HoverControl freeware Blackhawk and you'll get a big surprise.
Many of the frreware helicopters from HoverControl are superior to any of their payware equivalents.
I could go on, but you get the drift... I think I'd sum it up like this:
Those flightsim enthusiasts who joined the community because they wanted to fly airliners and have consequently explored both freeware and payware products will usually express their preference for payware.
Generally speaking I agree but... again there are exceptions as pointed out above by Welshflyer. Further, let us always be mindful that our die-hard airliner pilots have never or hardly ever flown anything else, this is especially true in the case of those who started out with FSX. It is also a fact that available 3rd party add-ons for FSX are scant when compared to FS9... so the 'noobs' certainly can't be accused of being narrow-visioned.
Ergo: IMHO the debate whether payware or freeware is better in general is and always has been futile. Thankfully we have both... and thankfully we are individuals.