Stich probably did have the most well rounded game. Having said that, Krajicek got to his A game the most consistently of the 3 (discounting injuries), he was also the most mentally strong by far.
Goran, was the least consistent, but had the single biggest weapon, and, was the best athlete, particularly in terms of movement. Stich was great in that department for such a big man as well, but not as much of a sheer jock as Goran. Krajicek was a touch heavy-footed.