It has HD Graphics, unlike the Wii...
I don't think it has over 640x480 (maybe 320x240?) pixels (unless you count every pixel twice due to the 3D... but it wouldn't be HD even then)
For example, a lot of NES RPGs are absent from the GBC, and for the GBA the sound quality for many game ports is crappy, not to mention I have yet to see classics such as Secret of Mana and Chrono Trigger for the GBA (although CT came out for the DS later).
My main problem with the GBA ports is the reduced screen size, and the ridiculously bright graphics in some games.
Weird I didn't see the bright graphics.
It's only present in a few games. Since the original GBA didn't have a backlight, they made everything too bright instead, making it look terrible on GBAs that have backlight.
I think its like 840 X 480 - total, the pixels per eye is half.