He does because even when he hasn't won the slams he has generally been the 4th person in the SFs. So relative to the rest of the field he was in the big 4 because he beat the lower ranked players just as much or almost as much as the others. The big 4 doesn't imply equality within that 4, it just implies that those 4 are all well above the standard of everyone else and so in practical terms are similarly difficult to beat for the #5 and below players.
Originally Posted by BedsheetRubber92
It's about competitiveness. Andy Murray head to head record with top players is what shows he belongs.
Murray vs Federer: 10-9
Murray vs Djokovic: 7-10
Murray vs Nadal: 5-13 (5-6 on hardcourts)
This isn't about legacy it's about form.
Murray has an almost 50% chance of beating the other three on any surface other than clay. This Shows that he is a contender with Federer Djokovic and Nadal. Murray can also be depended on to beat any other player outside of the top 4 and has made it to the semis 7 out of the last 8 times in slams.
Based on his current form, he is clearly in contact with Nadal Djokovic and Federer, and miles above the rest of the field.
If Sampras was still playing and losing the the top guys every single time would you really ever even think about referring to him as part of any top group?
Qouted due to making sense.