Recently, I been using REICAST from the play store, and I got to say it’s running smooth.
So what is reicast it is a multi-platform Dreamcast emulator. The project is currently in Alpha, usability, performance and stability issues are to be expected. Now animation games like Snk VS Capcom are glitchy at the moments, but as for sonic and power stone they are running very great with very little glitches.
You will need a Cortex-A9 dualcore, 1ghz+ is the minimum hardware for decent speeds. Now the Dreamcast BIOS is required for this emulator to work.
In the internal memory of your phone, create a folder named dc, make a folder named data inside it, and put the bios files there (dc_boot.bin, dc_flash.bin). If you are using a file manager, the path for the folder is /sdcard/dc/data/. You should dump these files from your Dreamcast, Google has many tutorials on how to or you can just visit emuparadise.me to get the bios files from. 
Now in order to save your game-play progress you will first need to format the memory cards. In order to do this you need to start the program, select the “boot bios” option, go to the “file” option, select the memory cards and then select the “delete all” option. So if you are looking to play some of your favorite dreamcast game, I would definitely recommend downloading this app for your android device or even the gamestick.
Download: reicast – a dreamcast emulator