I like the idea of old Mario games being converted to GBA, though I think they changed the games a bit too drastically and while I personally don't really mind the voices, I think they should've at least had the option of turning them off.
But yeah, words can't express how much I'd love a brand-new Mario game for the GBA. Although I suppose the high expectations for the game would be tough to live up to, Nintendo would probably rather focus on Mario 128 and not have to worry about making the best sidescroller ever.
However I hope Nintendo eventually releases a new Super Mario All-Stars game for the GCN. It should at least have SMB1, both SMB2's, SMB3, SMW, and SMW2:YI. It would make sense to put SMK on there too, and maybe even SMRPG if Square allows it. Also I think the game should have new enhanced versions of the games but also have the option of playing them in their original 8 or 16-bit forms. And voices should be added to the games but there should be the option of turning them off. Also wouldn't mind seeing the lost levels of SMB3 added to the game, along with some brand-new levels, as Worlds A-D. That would be cool, but I guess that's asking for too much. OK, I'll shut up now.