1973-73 lakers wrer 69-13 and an nba records 33 game winning streak
1972 dolphins 17-0
1985 chicago bears 15-1 super bow champs.
The 1972 Dolphins faced one of the easiest schedules in the league ever, and almost lost a couple of games at that. I don't even know if I would put them in the top ten best NFL teams ever.
I would go
MLB - 1927 New York Yankees
NFL - 1985 Chicago Bears
NBA - 1995-96 Chicago Bulls
NHL - 1983-84 Edmonton Oilers
For multi-year teams that had the same core players and had great peaks of performance I would go with
MLB - late 20's early 30's Yankees.
NFL- This is a hard one but I would put the 80s San Francisco 49ers over the best Steeler and Raider teams of the 60s and 70s. I could see a case being made for the Steers though. The cowboys are a little back and despite the multiple Superbowl wins the recent Patriot teams just don't measure up in a historic way. Besides one year (that they lost) they were never super dominate and a lot of their wins were done by the skin of their teeth.
NBA - Another tough one but I would put the Lakers of the late seventies and the 80s here above some of the good Celtics teams. The Bill Russell Celtics didn't have much competition outside of when playing against Chamberlain.
NHL - The early 80s Edmonton Oilers.
Best teams over the course of the sport
MLB - Yankees*
NFL - Close but I pick the Steelers.
NBA - It’s close but I just give the nod to the Lakers over the Celtics
NHL - This one isn’t that easy either. Maybe it’s the homer in me, and maybe it’s because a lot of the teams that were good decades ago haven’t been great in a long time but I would have to give it to the Detroit Red Wings who have won a lot and have are rarely bad or even go down to just average.
* The Yankees have had a huge unfair monetary advantage for almost a century now and have practically bought a good number of their wins over the years.