I honestly agree with this, the last Mario game I found new and fresh was Mario and Luigi: Bowser's Inside Story (2009). (The last mainline Mario game I found fresh was the first Super Mario Galaxy (2007).)
I mean, there was NSMB Wii and its four-player co-op, which had never been done before in a Mario game, but it felt like it was missing... something. I don't know what. A soul, I guess. It felt too perfectly calculated, too polished, too safe. Super Mario Galaxy 2 did have that soul again, but it was just more of the first one. It didn't blow me away because I had already seen almost everything the game had to offer before, it was just arranged in a new way. Unfortunately, the later NSMB games felt just as soulless. As for the 3D games...
I really don't dig the way Super Mario 3D Land/World try to be 3D versions of the 2D games. Platforming can't be as precise and skill-based in 2D and 3D, so they'll never be able to beat the 2D titles at their own game. The older 3D Mario games - 64, Sunshine, Galaxy, and Galaxy 2 - understood this. They totally reinvented what the Mario game was. I mean, really - think about how little SM64 and SMW have in common gameplay-wise. In World levels were a largely-linear track with a singular goal (though some levels had secondary exits); in 64 you explored wide areas to try and accomplish a variety of objectives. The means of combat were different - in World you just jumped, in 64 you could also throw punches and kicks. And the health system was reformed too - World had a system where powerups were health, while 64 had a more traditional health meter to account for the fact that a 3D world was less precise and easier to get hurt in. Though there was platforming in both, there was less of a focus on it in 64. Sunshine continued this pattern (though it was more-platforming heavy, with stuff like Ricco Harbor - and I think the game suffered for it. At least it did provide a platforming assist with FLUDD). The Galaxy games had more of a platforming focus, but it used a novel gravity mechanic to make use of the third dimension. The platforming was often focused on using the gravity mechanic to accomplish some goal, not making tight jumps like in the 2D games.
Also I'm just disappointed that we're not likely to see another game as off-the-wall and amazing as Paper Mario: The Thousand-Year Door (and this is coming from someone who really liked Super Paper Mario). If we just got another game as crazy-unique as that I'd be happy.
tl;dr I am le Mario defener
The Super Mario Galaxy orchestral music was awesome though