We've had lots of opportunities to demo our Stronghold robot. I always introduce it as "it was a medieval castle defense game. 3 on 3, red versus blue. We storm their defenses and shoot boulders at their castle." Pretty intuitive, and if you watch some match video, you pretty quickly figure out what's going on.
For Steamworks I've been saying it's a steampunk airship race. We need to pick up fuel and throw it in a boiler to build up steam pressure to launch our airships. Airships are incomplete so we need to grab and deliver gears to make the rotors turn. Finally we need to grab the rope to climb on board before take-off. All intuitive concepts.
2014 was inherently a very watchable game. I found this
2014 FIRST in Michigan championships video and despite it being an hour long, watched it all the way through like I was watching a football game. Any time I showed a segment of this to someone who had never seen FIRST or FRC, they got it right away.
2015... let's not talk about 2015.