Guess Wiki must be wrong so. I questioned 7 in my head when posting that but was searching on my phone on my way to work and that's what the link says. Re the Novak slam which I actually expected OTM to mention, I don't personally give it as much credit as I would have if he'd won it in a strong era/year 'cos the competition has been pitiful the last few years. I mean, sure, it was Nadal's fault he lost in the first round of the AO 2016 but the competition has still been woeful. Likewise, Nadal's wrist injury at RG 2016, again not Novak's fault, but let's call a spade a spade. Nadal was actually back playing well last year on clay and Novak's quest was made SO much easier with him out with the withdrawal after his wrist injury and facing Murray in the final. Federer was also very poor at Wimbledon 2015 and the 2015 USO final. Djokovic didn't need to play all that amazing to win at all. The year before, Novak was in his best form that I've seen though at Wimbledon 2014 and full credit to him there for the win but 2015 was a gift by Roger and same at the USO. He played like his true age/like turd to be honest so the Novak slam, while extremely difficult to achieve on paper, was not too difficult given how things panned out. No way Novak or anyone else, Federer and Nadal included, would have won all 4 in the era Sampras played in.
Re the 7 YECs, he won 5 YECs and 2 GSCs which were basically the same thing. You could argue the GSC wins are actually more impressive given the semi and final were best of 5 same way as Federer and Nadal have more difficult masters on their resumes than Djokovic, having won multiple back when they were best of 5 in the final.
https://en.wikipedia.org/wiki/Grand_Slam_Cup
https://en.wikipedia.org/wiki/Open_Era_tennis_records_–_men's_singles#Year-end_championships