The rule of thumb when it comes to comps is that the casinos give back some percentage, usually one-third. So if your goal is to get the room with as little expected loss as possible then whatever game offers the lowest house edge is what you should play. You will probably earn that room faster and with less bankroll volatility playing pai gow or pai gow poker. However the house edge is higher so your expected loss will be greater than in blackjack. In my opinion you should play whatever you would play if there were no comps at all. Then consider comps as icing on the cake.