I''m planning on making a YouTube channel where I play games and provide commentary over them. Can I legally monetize these videos?

You are a bit confused about the applicable law. It doesn't matter what YouTube "follows" -- what matters is the rights of the owners of the copyrights in the games you will play on the video. Under the Copyright Act, which controls, your video images of the games, with voiceovers, are "derivative works" -- a right which belongs exclusively to the copyright owners. Thus, your videos will infringe the copyrights in the games unless an exemption or defense exists. There does exist the concept of "fair use" in copyright law, but whether any particular use is "fair" is intensely fact-dependent. The notion that you will earn a profit from this activity suggests that your use is not "fair."