When people talk about "Mavs run was the best", I usually read it as "the ultimate David vs. Goliath" kind of thing, as opposed to them being one of the greatest teams ever. I don't know where they stack up in history's list of great championship basketball teams (in fact, I'd have to say they're pretty low, considering they were in the rare 'one true superstar' category).
For me at least, when I think of the Mavs' 2011 championship was one of the greatest, I'm referring to the backstory.
- Mavericks suffer heartbreak in 06
- Mavs flop in 07 (after finally beating the Spurs in seeding

)
- Dirk, and Mavs as whole, unfairly labelled as soft
- team is slowly built with a great cast of veterans, most slightly past their prime, who have never won a ring
skip to 2011 season
- Dirk had taken a pay cut so he could not only stick with his team, but to also allow for the signing of veterans, perfectly juxtaposed with "The Decision"
- fans start to believe after a great opening record, only to see Dirk get hurt and losing Butler for the season. Dirk's fine thiugh, thank God
playoffs:
- media and opposing fans again expect Mavs to exit early, even after the Laker sweep
- Dirk becomes Captain Clutch, wills Mavs past Thunder
- Game 1 against the Superfriends expectedly ends with a Mavs loss (a lot of Mavs expected the Heat to win, so I don't see where all of this "best team" stuff comes from)
- again because of Dirk, and concerted team defense, Mavs make what was then the biggest comeback in under 5 minutes in playoff history (yeah, yeah, until this year, Spurs), and get people believing
- through a great team effort, and Dirk again stepping up, the Mavs best the Heat, getting revenge for 06, and making a mockery of the whole "not 1, not 2..." speech Lebron made at the beginning of the year
Every fanbase would enjoy their team's first championship. Combined with the stigma the Mavs had for so long and that narrative, you can't ignore it was something special. For a team who's est feature for a long time was the logo, you take it when you can get it.
BTW, I know there are quite a few more reasonable Spurs fans that don't feel the need to tout "4 championships" every time the talk to a Mavs/ Rockets fan. I also know that the Spurs run a model team in terms of consistency and team execution (I daresay that the 2011 Mavs may have gotten a thing or to from how the Spurs play). It just gets annoying seeing things like "flagship" all the time, when the Lakers still have more rings in the same timespan (Tim Duncan era). The Spurs are elite, and they have been for sooooo loooong, but I would think the chest thumping would get old after a while.