I thought I'd share my attempt at creating a Genesis Bot here. Tried testing it using Aglar's Sonic 2 run, but unfortunately it desyncs at the end of Chemical Plant Act 2,
and I can't see any way to fix that. There is some slowdown that doesn't occur on gens, it's hard to notice but it occurs at 2:52-2:54, though it's not until the boss that it actually desyncs.
http://www.youtube.com/watch?v=Dnt0-CAui2Y
This was made using a Genesis Model 1 VA6, two controller extenders, two DB9 gender changers, a breadboard, an Arduino Mega 2560, an adafruit MicroSD breakout board, two 74HC157 multiplexers, and many jumper wires. The Arduino sketch I wrote myself, but for stripping lag frames I just slightly modified the Lua script made for the NesBot to work for the second controller.
Here's the files in case anyone wants to look at them. Hopefully someone who has more of an idea of what they're doing than I do can help. I haven't tested it very much with any other games since my Genesis library isn't very big.