So the comment that intrigued me the most from the initial thread was the 'attitude of a champion' bit - because this is a characteristic that *feels* like it can be compared across generations. Here are a few I would place in that rarified category, who didn't necessarily have the results: Chang, Muster, Hewitt, and Roddick. Chang just didn't have the game to match Sampras. Similarly, Hewitt didn't have the game to match Fed. For that matter, neither did Roddick. I also find a similarity between Safin and young Agassi - incredible potential negated by lack of focus. If anything, Safin had greater potential. Another key difference is that while Agassi found himself late in his career, Safin retired. During their early years, don't think either had the 'mentality of a champion', even though both won majors.
Roddick is interesting to me, and many will likely disagree, but I see him as Multi-GS winner in other eras. But his game was seriously deficient against Fed.
Maybe the point of all this is that I don't think the MASH generation is as bad as Babble makes it out to be, with Roddick and Hewitt both possessing the attitude of a champion. I'd also put Ferrer in that category, somewhat like Chang. Though he might be in a different generation
One more angle to this - big losses to guys who *do not* have the attitude of a champ. I'd put Krajicek into that category, as well as Berd.