Personality is the number one most important thing for me when I'm watching gaming channels. I will watch SeaNanners or Gassy or Nogla or any of the other hilarious folks out there even if they're playing games I'd never want to watch/play. Now if they end up playing something awesome then that just adds to it and makes it even better but personality should definitely be your priority.
Gaming channels are entertainment channels after all, and the unique entertainment value that a gaming video has over simply playing the game itself is the
person playing it - so ensure you have that part as your focus and people will stick around. This also has a positive side effect that people who perhaps came to your channel to watch a specific lets play, will be tempted to watch videos of other games on your channel just because they get hooked on how funny/interesting/etc you are.
It also depends on the kind of games you're playing. If you're playing casual type games, make it funny, joke around, play with other people who're also featured in the video (one funny person = funny, two funny people = hilarious, etc, you get the idea, comedy is made better by good chemistry between people).
If you're playing something where more strategy is involved, like maybe one of the Paradox games like Europa Universalis IV or something, then what I look for is someone who describes exactly why they're doing what they're doing very well. So many times I'll find a good EU or Victoria video but the person doesn't explain a single one of their decisions, so some of the more advanced strategy goes right over my head and it's not as fun to watch. The people who take their time to really explain things make it a lot more enjoyable because you can start to get in the same mindset as them, and also learn to play better yourself while watching.
If you're playing horror games or other games where people are watching partly to get scared with you or to see your reactions etc - then pick games that
genuinely scare you. So many people fake reactions to horror games without being scared. Don't be one of those people, find a game that genuinely makes you jump or at least creeps you out, turn off all the lights or maybe light a candle or something, shut the curtains, do the whole "I'm about to watch a horror movie" kinda setup, and get into it. It makes it more atmospheric and enjoyable to watch when both the viewer and channel owner are getting scared.
Etc
