I don't think investing in gaming startups is about getting a return from a 100m or 1b company.
It's about investing in games. I think an individual game is analogous to the typical startup. Minecraft is a $2.5b one[1].
Here's a list of 11 games grossing $3b or more: http://www.businessinsider.com.au/the-11-top-grossing-video-....
Riot Games had $1.3b revenue in 2015, and has had VC funding. I think that's what you're asking for.
[1] http://recode.net/2014/09/09/game-on-why-microsofts-2-5-bill...