Conclusion
You could categorise the accomplishments of each team discussed here separately, as per the consistency of each team or the enormity of it.
Chelsea and Manchester United both enjoyed years of competition and dominance with one year in particular standing out for both teams as their greatest. Consistency is one of the key elements in leaving a legacy which would want to be followed.
Arsenal and Arsene Wenger peaked massively in 2004 and nothing he could do after it would be able to match the standards set by this incredible team. Manchester City are in a similar vein that they have done something that may only happen once in the history of the Premier League, and they are not going to match the same levels that they reached this season in the next.
If Manchester City continue to play this brand of football under Pep Guardiola and stay at some of the lofty heights they reached this season, though, you cannot look further than them as the best Premier League team in history.
I feel they have already achieved that, as some significant records have been going tumbling down all season. If they even manage to hint at reaching similar heights in the upcoming seasons, City's current class will be hailed as the greatest team in Premier League history.