There are 2 different ranks for the Arcade section. The first one is the obvious one, who has the most high scores. The top 3 users are listed right on the main arcade page. The other ranking is the League Scoring.
Here's a link to the leaderboard. The current table scoring is:
1st: 20 points
2nd: 10 points
3rd: 8 points
4th: 7 points
5th: 6 points
6th: 5 points
7th: 4 points
8th: 3 points
9th: 2 points
10th: 1 point
Only your best score counts for each game.