Not saying that Super Mario 3D Land is a bad game (I loved it), but you're comparing console games versus handheld games. DS Mario sold way more than the 3DS Mario games, just like how Wii Mario games have sold way more than Wii U Mario so far.That was >6 months ago:
Mario 3D Land could be at 10 millions now, and it will never stop selling. It's a sizable increase vs Mario Galaxy 1&2 sales.
Besides sales, most people loved Mario 3D Land, as they loved previous 3D Mario games.
So factually, you're both wrong.
The sales are still fantastic though.