This is a fact so many people don't seem to get, especially when asking for classics on handhelds, like GBA games on 3DS or PS2 games on Vita. "But the Vita/3DS is more powerful than the GBA/PS2!" Yes, but what you don't understand is that your Vita/3DS has to be powerful enough to pretend to be that system it is emulating while still being a Vita/3DS. It is a lot like running a windows XP virtual machine as a separate window on a Mac, it takes much more to get it to run than it would to just get XP to run on that machine.
All that said, I would love PS2 classics on Vita and GBA games on 3DS, but I also understand that these things are difficult to implement and that there can be good reasons why they don't work already.
P.S. No the ambassador games don't count as 3DS running GBA games, this is a convoluted hack that tricks your 3DS into thinking it is a DS running a GBA cart, and does not allow any Virtual Console conveniences such as saved states, as well as has many bugs. No way Nintendo wants to release more games in this sad state.