hmmmm... this is a good question. these questions, obviously, are always subjective. none of us saw the great teams of the 70s, didn't really get a full grasp of the 80s NWA teams of Road Warriors, Midnight Express, Rock & Roll Express, or the Freebirds in Texas.
1st team came to mind was the Hart Foundation. then I think about Tully & Arn, don't think I've ever seen them have a bad match, and they had great psychology. The New Age Outlaws were probably the most popular team ever. the Rockers might be a bit underrated.
in the end, I think its the Dudley Boyz. they had success everywhere ECW, WWF, NJPW, TNA. I have no doubt if they had gone to WCW, they would have been champs there as well. they were innovators, the were the missing ingredient in the Edge & Christian/Hardy Boyz feud. they wrestled hardcore matches, but didn't have to, they could have solid matches without tables and shyt.