I don't know how well the Fallon demo really does at selling people on the game that didn't know about it. We get four minutes of Reggie trying to rush him through the level and explaining that the cat-suit is the "big innovation" in this title. Just feels kind of underselling...although to be honest Jimmy Fallon annoys the hell out of me anyway so maybe that's part of my issue.
I have no doubt that this game will be fun and have the varied and interesting level designs that we know EAD Tokyo is capable of, but I do somewhat agree with the people that aren't totally hyped for this, either. In my case, I feel underwhelmed that it feels like the Mario series has, in recent years, sort of turned around and started backtracking when it comes to world presentation and the "expansive" nature of Mario. Going from SMB3, to World, to 64, to Sunshine, each new Mario game brought along this sense of constancy to the setting you were exploring, there were real themes to the locales, and twists on those themes. Courses in Mario 64 and Sunshine were revisited and allowed for little subplots and minor characters to make a real presence, and it made those worlds more memorable. The first Mario Galaxy was kind of the inflection point, as the "series of planetoids" idea allowed the team to free up gameplay from a thematic standpoint, but it started coming at the cost of familiarity with the world. Galaxy 2 took that idea a little further and brought back the grid-style level select, and then 3DLand just gave you a "map" consisting of nothing but a straight line to plow through all of these completely disjointed levels in a very linear fashion. No more course themes or galaxy names, we're right back in the days of 1-1, 1-2, 2-4, 4-airship, etc. Mario 3D Land was good, but the game as a whole feels far less memorable to me because the whole thing is just this series of disjointed platforming challenges. I believe that with the addition of 4-players, we're going to continue in that direction, treating the series simply as a collection of flagpoles to be reached, rather than a whole new world to adventure across.