There have been forums filled with these comparisons, especially this one, but just another try:
What's the best rider? There is no global consensus. Some value one aspect of riding more than the other, and a points system doesn't say it all (like you mention MvdP being 15th in PCS).
For me, a best rider is someone who is a complete rider that can win everything in every way on every terrain, that can climb, sprint, is good at bike handling, positioning and can lead the group he is in e.g. on a technical downhill, that can carry the weight of a race if there is no team around him, create decisive moves either mid-race splitting up the peloton, or at the end of the race going solo, can defend well without always having to rely on other riders, his team, performs well in every race he's taking part in, rides from February to October, ...
I was going to discuss in detail what I think are strong / weak points of the riders you mention (compared to WvA), but I'm afraid I will get dragged into a fanboy discussion about each of these riders (except Pogacar, in which I cannot detect real weaknesses, only maybe slight disadvantage vs WvA with regards to flat sprinting and flat TT but nothing else).
So I'll focus on WvA in a positive way:
WvA is a complete rider in most areas except GT riding as he is a limited climber. Notwithstanding his low win rate this year, in all races that mattered, he was either the best rider in the race, whether or not on par with another rider (think E3, GW, Roubaix), or within the top 3 with only MdvP and Pogacar being clearly superior (RVV, MSR) in some races. It's hard to be named the 6th best rider in the world, if all you ever did was finish 1, 2, 3 or 4th in every race you targeted, but anyway.
WvA has been (and I'm not saying this, most pro riders say this) the strongest rider in the TdF in 2020, 2021, 2022 and 2023: he decided singlehandedly if a break was allowed to go, if he was going in the break, he pulled for ages at the front of the peloton, won some TT and sprint finishes in between,... He was and is massive. He does most of the decents in the mountains / hilly stages at the front of the peloton when Jumbo is pulling. No other rider in the TdF does the same amount of work AND is winning stages at the same time.
If I have to evaluate who is the strongest rider in the peloton, I refer to these comparisons below and especially the graph and the points / km. Based on these, WvA is worse than Pogacar (with Pogacar being the reference point and the very best rider since... Hinault? Merckx?), just a little worse than Evenepoel (but the trajectory of Evenepoel is not consolidated yet: if he keeps on going like this, he's clearly better, but if he deteriorates just a bit, he's on par with WvA but not really better), on par with Roglic (but Roglic has and will have a shorter career), but he's better than MvdP and Vingegaard on these stats. Stats ofcourse neglect that WvA doesn't have the same number of big wins like Pogacar, Evenepoel Roglic, Vingegaard and MvdP, but compared to WvA, some of these riders are far less complete (in terms of what I mentioned above), and much more of one-trick (or some-trick) ponies. People on this forum keep valuing one-trick-ponies more than complete riders, fine, but to state that this rider is better or worse than that rider is a subjective excercise. I made mine here, but at least I back it up with some arguments (ofcourse, some of those are my personal opinion) AND stats (again, some of those stats are not important for those who value big wins over something as abstract as points, but imho, points reflect how much a rider puts effort in his races, and how much a rider is present in races. You have much more TV time of someone like WvA, Pogacar and Evenepoel as these riders attack solo much more often, compared to Vingegaard and Roglic for example, and this (subjective) feeling reflects in the (objective) points ranking.
If you would make a spiderweb diagram of all of the riders mentioned above, Pogacar's will be perfectly round, WvA will be round except for climbing, and all others will have gaps and spikes here and there. In terms of well-rounded riders, WvA is among the very best. If you keep saying he is the 6th best, watch the Tokyo Olympics again, or Roubaix this year, or every single TdF stage last year (and most of those this year). For a 6th best riders, he is surely hurting the 1st, 2nd, 3rd, 4th, 5th (however those might be ranked)... a lot of times in a lot of races.
Head to head career results between Wout van Aert and Tadej PogaÄar. The overal score is 39.2% for Wout van Aert versus 60.8% for Tadej PogaÄar. A comparison on same race results, time trial points and the points per age.
www.procyclingstats.com
Pogacar clearly wins. Points / km stellar by Pogacar: 23.9 (WvA: 20.9)
Head to head career results between Wout van Aert and Remco Evenepoel. The overal score is 53.3% for Wout van Aert versus 46.7% for Remco Evenepoel. A comparison on same race results, time trial points and the points per age.
www.procyclingstats.com
Evenepoel slightly better in his trajectory, but it's still a very short one so we'll have to see. Points / km =20.3 is almost the same WvA: 20.9).
Head to head career results between Wout van Aert and Primož RogliÄ. The overal score is 44.6% for Wout van Aert versus 55.4% for Primož RogliÄ. A comparison on same race results, time trial points and the points per age.
www.procyclingstats.com
On par with Roglic, but WvA shouldn't deteriorate in the coming 2 years. Points / km 15.9 (WvA: 20.9)
Head to head career results between Wout van Aert and Mathieu van der Poel. The overal score is 56.4% for Wout van Aert versus 43.6% for Mathieu van der Poel. A comparison on same race results, time trial points and the points per age.
www.procyclingstats.com
WvA clearly wins. Points / km = 16.6 (WvA: 20.9)
www.procyclingstats.com
WvA clearly wins. Vingegaard has never done a season as good as WvA. Points / km = 12.9 vs. 20.9 for WvA.