I think it's bullshit that devs give cubers half-assed efforts and then blame the fanbase for the sales, and pull support.
Multiplatform games that WEREN'T butchered on the cube that actually sold well:
Burnout
Burnout 2
Prince of Persia: TSoT
Metal Arms: Glitch in the System
Alien Hominid (sold better than the Ps2 version about 2:1)
GOD: DAMM (sold 500k+, but only ~50k on Xbox. Granted, it was a timed exclusive. And then Atari says GOD DAMM 2 is Xbox exclusive. Why? I don't know.)
I do believe Beyond Good & Evil performed fine on the Cube compared to the other consoles
The Harry Potter Games (ok that's because GC is teh kiddie)
MMAC (and despite what people say, I still think there's nothing wrong with the controls)
Sonic Heroes
Phantasy Star Online (all of them)
Timesplitters 2
Viewtiful Joe 2 (yeah, it bombed, but it sold better than the Ps2 version)
Hell, I even think the original Splinter Cell did moderately well on the Cube.
Now this isn't to say that Cube games were a gold mine for multiplatform releases, because, for the most part, cube sales were not the highest. Ps2 sales were, and then the Xbox and Cube fought it out for 2nd place on many games (except for the sports games)
It's when developers started choosing to put online in the Xbox and Ps2 versions of games while giving the cube version some stupid play chooser via GBA connectivity *coughmaddencough*, when they started releasing the cube versions of games 3-6 months after the Xbox and Ps2 versions, and when they started giving cubers glitchy, unpolished versions of their games which had entire gameplay modes removed (*looks at Splinter Cell 2 and 3*) when the third party sales REALLY went into the shitter.
For the most part, until about mid-late 2003, multiplatform games sold about equal on the cube and Xbox. That's when developers started giving the Cube the shaft, and also around the time Cube 3rd party sales slumped.