Going by how VC usually goes, here's my breakdown of 3DS GBA VC by region:
JP - at least 2-4 GBA games a month, all of decent to excellent quality, along with a good amount of games from the other represented consoles
EU - Around 1-3 GBA games a month, mostly Nintendo's own games along with a 3rd party gem every once in a while, games from other consoles are still represented but not as much
NA - 1 GBA game every 5 or 6 weeks, with most of them being of less than desirable quality, and releases from other systems drop considerably. Will be behind other regions by about 20-30 titles by the end of 2013
I'm bitter :<