If I won I would say:

    "Nice to meet you..I hope we not face again...such an easiest game.bye2"

if i lose i gonna say:

    "Nice to meet you...you should thanks to me because I help you to win..truthly,the game we had before is the most boring game in my life so i let you win..bye2.."

hahaha..the words above is just a kidding..foe your information I never used the words above..hahaha..what is your popular words when you finish a game?Tell us..... 

Jokes aside, when I win, I quite often send a separate message to my opponent thanking him for the game, often with one or two uplifting moments.  When I lose, I invariably congratulate my opponent, as I am about to do with you

When i win: Sorry ...... and good game.

When i lose: Good game.