No no no no no no no (with apologies to Jim from the Vicar of Dibley).
This answer is fairly obvious in regard to functionality and user interface but I'm really referring to viewing quality. I've tried quite a few over the years but the one I'm currenty using is FastStone Image Viewer which was suggested by a fellow CiC member. I think it's pretty good in terms of viewing quality and functionality. I do believe that not all viewers are equal when it comes to viewing quality.
I guess I've had this sort of intuitive feeling in the past that displaying an image is a fairly straight-forward task in software - decompress the jpeg and "map" the pixel details to the screen. But I think there's more to it than that (eg image scaling, filtering and whatever else is done inside the bowels of the software).
I wondered what others thought about this subject.