Ranking based on games played or won rewards grinding AI0 (it loses the fastest). The current system, based on score, rewards grinding the AI with the highest expected return per minute (and usually skipping the spins -- but maybe not, if you expect the cards you'll win to help you significantly improve your rate of return). Ranking based on games lost punishes grinding, and is the only single-total ranking of the four that puts player A ahead of player B. However, ranking based on the ratio of any two of these four totals also puts player A ahead, by a factor of 20/9 (2.222) to 125/3 (41.667):
Score: B's score is 6/5 (1.2 times) A's score (A 10,000 vs. B 12,000).
Wins: B has won 6 times as many games (A 500 vs. B 3,000).
Games: B has played 40/3 (13.333 times) as many games (A 600 vs. B 8,000).
Losses: B has lost 50 times as many games (A 100 vs. B 5,000).
Wins/games: A is 20/9 (2.222 times) as good (A 0.833 vs. B 0.375).
Games/losses: A is 15/4 (3.75 times) as good (A 6 vs. B 1.6).
Score/wins: A is 5 times as good (A 20 vs. B 4).
Wins/losses: A is 25/3 (8.333 times) as good (A 5 vs. B 0.6).
Score/games: A is 100/9 (11.111 times) as good (A 16.667 vs. B 1.5).
Score/losses: A is 125/3 (41.667 times) as good (A 100 vs. B 2.4).