I think it's imporant to separate PvP and PvE statistics (just going off the current system). Maybe even make the leaderboard sortable to account for differences in 1v1 battles versus 5v5 or 25v25 type battles as statistics will vary greatly in these.
In general - Total number of battles, Average Accuracy, Win/Loss ratio, Average Damage (make this sortable by ship class and battle size), Average Battle Size, Ships Sunk/Captured and maybe Damage Received.
The same could be done for guilds by showing the Total number of battles, Win/Loss ratio, Ports Captured, and Ships Sunk/Captured
A Daily Leaderboard and an Overall Leaderboard would be nice as well. Perhaps even add in a Records section for things like "Most Ships Sunk in a Day" and "Most Damage in a Battle with X Ship" as this would encourage competition. All of these could be tracked at the Individual and Guild level and for Daily and Overall.