Ooooh-kay... where did my post go?
Anway, yes there are GB/GBC emulators. For GBA, you need a slot 2 card such as the EZFlash 3-in-1. Next time, use Google for Gods sake.
Edit: Oh, the OP made 2 posts. So not only did he not Google but he made 2 useless topics that have been answered 100,000 times. Yay!