It really grates me when England win and Australian commentators make excuses but make rubbish excuses as to why we couldn't possibly play it at a sensible time.
It's an embarrassing, arrogant attitude. Anyone using the 'Manly were underdone' excuse is kidding themselves, Manly should have prepared better.
I think it might stem from the Australian national team doing well over England, and from the greater mix of teams that succeed in the NRL, suggesting the NRL has more depth than the SL.
But, the Australian team doesn't have it all its own way, and a few key individuals could make a difference. We all thought our cricket team came from a better "system" when it turns out it was just a few very good individuals that made us good 5 years ago, and now England are better.
In regards to the NRL competition vs the ESL, we can never truly know which is best but the top ESL teams have competed very evenly with the top NRL teams for years, and home advantage and an extra 2 games preparation can't explain all of that. The salary cap in the NRL accounts for the more even mix (when its not being rorted) as it is not even in the ESL. But that doesn't necessarily mean the lower NRL teams are better than the lower ESL teams, but they possibly are if more money is spent on them.
As LeedsStorm points out, Super League players have to play more games, and the Super League games seem to be played at a cracking pace. The best Super League players who do come to the NRL (in the last decade or so) have done very well in the NRL, and even though a large number of NRL players go to Super League, only a few of them actually stand out.
So I can't see why we can't just accept the competitions are close, the WCC is flawed but exciting and as good as we can expect (though I'd love more teams like in the Super League season in Australia, perhaps every couple of years!), and the best SL teams and players are world class and good to watch, just like the best NRL teams and players.