I like to think of it this way :
"If you have to think about what games to play for your gaming channel then are you sure this is something you should be doing."
Look at some certain youtubers for example. TheRadbrad or Christopher Odd Lets play all games and were lucky enough to get it easier then others (of course with a serious amount of consistency and hard work). Captain Sparklez or DanTDM just play minecraft. So people know what to expect. CenterStrain01 (one of the smaller channels of the past 4 - 5 years has recently hit a growth spurt and is known for his stealth gaming. He is most famously known for his splinter cell playthroughs. I'm not trying to promote but what I would love for people to understand is that no one person can tell you what game somebody is going to be able to play to catch an audiences attention. If I could give any sort of advice it would be to play something you are good at. If somebody stops by and your comfortably talking about a game like you understand it and stuff they will stay faster then they would if your just sitting there trying to come up with sentences for a game your not good at. Even so don't force yourself to play games you don't like just because other people love them. Hope this didn't come off as a negative post I would love for everybody to reach the potential they can you just got to find it first