Nay, Mario is stronger than ever.
He's already at 1.5m on a system with just 2.5m. If anything, the sales are because of Mario. Let's do a fun comparison however, just to see if it's actually true what I just said. Since you can go back to the launch of the original GameBoy in Japan on this site, these are the Mario launch title sales, first week Japan. Complete with attach rates (for the JP numbers), calculated by my own mathmetic wisdom, from the numbers I find here. So, believe with caution. Additionally, the last two are global sales for combined first weeks, as that's available from the launch of the DS onward. Everything's dug up out of the weekly sales charts:
- Super Mario Land: 86,283 (AR: 91.1%)
- Super Mario World: 180,187 (AR: 99.4%)
- Super Mario 64: 292,310 (AR: 97.3%)
- Super Mario Advance: 228,356 (AR: ?% (no HW numbers))
- Super Mario 64 DS: 138,438 (WW: 501,138) (AR: 30.2%)
- New Super Mario Bros. U: 166,572 (WW: 559,436) (AR: 54.3%)
So, sadly the only one missing is the original Super Mario Bros. on NES. It looks to me as Mario as a WiiU launch game has performed about average, almost as much as Super Mario World on the SNES. The latter however was bundled, while NSMBU is not. It achieved it's sales 100% on it's own merits. It's fourth place out of seven titles; exactly in the middle. Unfortunately, Super Mario 64 on N64, also not bundled at the start, seems to have been a beast (and rightfully so ) so it didn't get anywhere near that, but we sadly don't have worldwide first week numbers. I'd have loved to have seen and compared that.
Also, I don't know if the numbers for the older generations are reliable. When you read them, you'll know why. Software numbers are believable, but the attach ratio is ridiculously high. For the N64 it's still possible though as it launched with only two games. Personally I thought there was also a console-only SNES package, I guess it could be that this was not until later in the game. If so, SNES attach ratio is also true.
~Bonus:~
- Luigi's Mansion: 160,312 (AR: ?% (no HW numbers))
- The Legend of Zelda: Twilight Princess: 146,367 (WW: 716,111) (AR: 40.1%)
So yeah, Mario was the decent choice as it beats the other launch titles Nintendo tried in Japan at least. For worldwide though, Zelda would've been better apparently!
EDIT: Attach rates for the Japanese numbers added to paint an even clearer picture. Conclusion doesn't change however.