I would tend to agree that Pong would be easier than Asteroids - think about the asteroids breaking apart, the hyperspace, the shooting, and the space ships that appear all requiring physics and AI - you can get away with a basic Pong game with no physics at all - and if you make it two player only (which is how Pong should be played) then there is no AI at all to consider.
Go on - you know it makes sense - go for a Pong game first
If you do want a single player Pong game then the AI can be simply determing where the bat has to move to intercept the ball and making it move that way.