Since it came out, the R-Pi2 has been a god send to those wanting more CPU Power and Speed with double the RAM and a Quad Core Processor. But it needs the newest of the Raspbian Operating system (Wheezy, released in 1/2015 and now Jessie, released in 10/2015) and it will not work on the older Raspbian Releases.
 
Hence the problem: All known Emulation releases: RetroPi, Mame4All, Chameleon Pi, etc, et al; all are based on the older release of Raspbian that will not work on the R-Pi2.
 
PetRockBlock released the Beta of RetroPi 3.0 for the R-Pi and R-Pi2 in May/2015. It lets you store your ROMs on a USB Stick instead of the SD Card of you want, but it needs a root directories on that USB Stick set as /RetroPie/roms/  . It is still buggy. Since then it has release 3.1 and 3.2 with fixes to a lot of those bugs.
 
The current version RetroPi v3.2.1 for the R-Pi2 is 762MB in size as a compressed file and installs to an SD Card like the other versions out there. Whether you want your ROMs on the SD Card with RetroPi or on a separate USB Stick is on you.
 
But, there is 2 different versions - one for the R-Pi's and another for the R-Pi2's. The way it is set is that it will only work on the assigned system and not for each other. Though this brings emulation for the R-Pi2, it forces you into using one or the other exclusively. Note: with a few modifications to the Boot Programs, you can boot the Banana Pi with the Older RetroPi, the RetroPi for the single core R-Pi's and the RetroPi for the quad core R-Pi2. Banana Pi Users have been using RetroPi and the other emulation packages in this manner for years and have enjoyed using the 1GB and Dual Core CPU the Banana Pi has over the slower single core R-Pis. CD ROM emulated systems like the Genesis and Playstation emulations run a lot faster and cleaner on the Banana Pi. For the new R-Pi2, similar or better results should be expected.
 
Download Link:
http://blog.petrockblock.com/retropie/retropie-downloads/
(The top link is for the regular R-Pi single core and 512MB RAM, the second link after it is for the R-Pi2 with its quad core CPU and 1GB of RAM)
 
Information Link:
http://blog.petrockblock.com/retropie/
 
Note: I'm only downloading the version for the R-Pi2; I already have an older version for the R-Pi which works fine for most of my Emulation Needs.

sounds great
1 let me know how well it works. looking to uild an arcade as a gift if I can get a few bucks.