Arena of Valor, most popular mobile MOBA game; 80m daily players as of Dec 2017 and I believe it's currently the biggest game worldwide despite mostly being popular in China (I think there are even stories of politicians delaying press conferences to finish a match lmao) - developed and published by Tencent
Fortnite - Tencent owns 40% of Epic Games
Clash of Clans - Tencent owns ~85% of Supercell
PUBG - They're working on acquiring 10% of Bluehole, developed PUBG mobile, and managed the (hugely successful) China release
Overwatch / Hearthstone - Tencent owns ~5% of Activision (about $2.5b)
Crossfire (still very popular in Asia) - Tencent managed the China release
Candy Crush - Tencent is the distributor in China
Some smaller but also well-known companies:
Path of Exile - 80% stake
Miniclip - majority stake
Ubisoft (Assassin's Creed, Far Cry, The Division, Rainbow 6) - 5%
Paradox Games (Cities: Skylines, Stellaris, Crusader Kings, Europa Universalis, etc) - 5%
Netmarble Games (mobile games like Lineage 2, YS Online) - 22%
(mostly sourced from https://en.wikipedia.org/wiki/Tencent_Games)
This is completely ignoring their significant shares in Tesla, Snapchat, etc. And the fact that they're like, not an actual investment firm and have their own business, including WeChat, QQ, and their AI lab. League's decline in popularity is certainly bad for them, but relative to their entire operations it's only a small hit. This recent drop in market value is, in my opinion, better attributed to the doubts over tech stock valuations due to Facebook and Twitter.