In Sampras' time, it was much more difficult to be good on all surfaces. There were a lot of clay specialists as well. I would still put Sampras above Nadal, even if Nadal has 1 more slam. The week in no.1 stats, no. of YECs, and YE#1 should also be considered.
You forgot Nadal's advantadge with the Olympic Gold Medal (Sampras participated in Barcelona 92) and the 30 Masters 1000 (even Agassi won more Masters 1000 than Sampras). Anyhow, I disagree. For me, all the things you mention would be relevant only in case they were tied with the same number of Grand Slams. Then the second criterion would be to see who has the Career Grand Slam (because it shows one player was more complete than the other).
Greatness' criteria in order of relevance:
1. Number of GS titles
2. Career Grand Slam (only necessary if they are tied in GS titles)
3. It would be largely debatable (but this criterion would be only necessary if the players are tied in the criteria 1 and 2)
Let's see how to apply these criteria with this example:
Player A: 30 Masters 1000. 3 Grand Slams.
Player B: 0 Masters 1000. 4 Grand Slams.
For me, the player B is better. The most important criterion is the number of Grand Slams.
Let's see this another example:
Player A: 30 Masters 1000. 4 Grand Slams.
Player B: 0 Masters 1000. 4 Grand Slams.
Player A is better. We can see other factors/criteria only in case they are tied in GS titles. A greatness' criteron must be universal. Otherwise, the discussion about ATG would be very subjective and anyone could argue his favorie player is better than others taking under consideration the criteria they want.
If you disagree, what would be your main greatness' criterion?