Channing Tatum's probably the best actor/dancer combo. No idea what his vocal cords look like though, and I always care more about the singing than the dancing.
Those comparisons are unfair (I am talking about the YouTube clips) because they're not the same kind of dance scenes. The ones you posted are dance numbers being filmed. The whole point of them is to have someone dance on set and follow them along with the camera. All the musical scenes in LLL are about the story, except for the first one. The opening is about spectacle, and the explosion of colours, the camera pirouettes, the extravagance of it all are at least as important about the quality of the actual steps. The second song is about the party side of LA and the life of people who live there and places Emma Stone in that context, as someone who wants to make it but feels alone and isolated. And so forth. Every other song progresses the romance or brings something to the story. It's never just about dancing. In fact, yeah, the dancing is often pretty basic, but that's not the point. The observatory scene is about that space background more than what the black figures are doing.