I would think any kind of legitimate publication would count as something unusually good before grad school. of course there are programs, in which students are guided through relatively easy research projects by a researcher, and it results in a joint publication, and these might mean somewhat less, but even so, it is a good experience that I would think is relevant to the grad school experience.
as to the gre,it seems that my dismissal of them as almost a joke for grad school admission was based on the level of the general one, which is apparently just another sat test.
most people agree the subject test is harder and is a useful test of the topics taught in a typical undergraduate major. i still maintain however, that admission to top schools is based on something else entirely, something less cut and dried, something hopefully deeper, the opinion of teachers that an applicant has the potential to excel in the world of mathematical research.
this ability is something I feel when talking to a student, and noticing that they catch some relevant significant point more quickly than I do, or generate some original idea that impresses me.