This is something I have suggested before but I think would be a very simple and valuable addition - a best ever rank for each game in your stats calculated by taking what percentage of players you are better than at any moment and recorded by the rank you achieved.
For example, say at Go I was ranked 100th and 1000 players were ranked at the time (0.1) but I subsequently lost position and the player pool sank, say I was 150th out of 600 (0.25) - then my stats would say
ranked 150th (best 100th).
By keeping a permanent record of a player's best achievement you not only add a nice element to the stats but you also tackle some of the issues with people clogging up the top end of the leader boards. If I get the no.1 rank when a game is just developing I don't need to sit on my Elo points playing just one game against a weak opponent every so often to maintain it - I can carry on playing and even if my rank falls I will still have say current rank 62nd (best rank 1st).
For example, say at Go I was ranked 100th and 1000 players were ranked at the time (0.1) but I subsequently lost position and the player pool sank, say I was 150th out of 600 (0.25) - then my stats would say
ranked 150th (best 100th).
By keeping a permanent record of a player's best achievement you not only add a nice element to the stats but you also tackle some of the issues with people clogging up the top end of the leader boards. If I get the no.1 rank when a game is just developing I don't need to sit on my Elo points playing just one game against a weak opponent every so often to maintain it - I can carry on playing and even if my rank falls I will still have say current rank 62nd (best rank 1st).
I was top 5 at bubblee pop and this achievement is lost from history. Well, I have screenshot left 
and I use think how nice it would be to have it recorded. Please note - nice to have. Not like goal of life or so, but I would truly appreciate it and it would be more fun to reach higher and higher.