This has happened to me before and can be quite annoying. I try and put it out of my mind ,but if it bugs you I would ask a question and ask him/her on their thoughts.
This will either go two ways but it will make them pay attention as they wouldn't of expected that. It is letting them know subtly that you were aware that they weren't paying attention. This is a good thing to do anyway as it will increase awareness and others who were drifting off will wake up.
In future try and bring the audience into your presentation so that there is no opportunity to do other things .
It depends on the category of people you are giving this presentation to. If they are some bunch of adults, then it definitely wouldn't be polite to ask them to stop making use of their phones in the presence of everyone. You may just get yourself embarrassed. But if they're some kids, you can politely ask them to stop making use of their phones and play the games later. And if they are really cool little kids, you can go ahead and seize the phone if you feel they are a disturbance to your presentation. Another option is for you to simply ignore, as long as the game doesn't produces some sounds that hampers your presentation time.
If this was happening to me, I would try to grab that persons attention in a humorous way. I think that saying something silly, or ridiculous in the middle of the presentation can lighten the mood, and get people to pay attention a bit better.
In your example, I would mid-speech throw out something like this - "... And I would just like to inform you all that I have authorised a $1 million dollar pay-rise for Joe" (the game playing phone user) At that point stop for a bit and wait for the reaction. If Joe doesn't respond, his colleagues will and that will draw Joe's attention back to you. Brush it off with a ha ha - you wish type comment and move on.
This way, no one's feelings are hurt, the tone of the presentation lightens up a bit, everyone has a bit of a laugh and Joe starts paying more attention.
i guess there is nothing really you can do, people have different attention span. Its just one person, so it may not necessarily mean that you are boring.
Although Depending on the kind of presentation, i'd try and call for the persons attention.
For instance if it were a school presentation, i'd make it more engaging, ask questions and ask for their contributions, and generally just get them talking and participate. That in many instances has always made my presentations more engaging, not giving room for anybody to be on their phone.
If you're giving a presentation and someone isn't paying attention and is doing something else, for as long as the thing the person is doing is not distracting you and other people paying attention, you can let such a person be. But if you're not cool with what the person is doing and the person isn't your superior in office, you can simply say "Mr. A, I'll greatly appreciate it if you can give us you attention". Just try to be polite without sounding angry or authoritative. You'll get the person's attention
In my own opinion, If that thing happens again and if you seemed not to like what the person is doing, I think the best thing is to warn the person to stop playing with his mobile phone. Tell the person to stop playing with his phone 📱 or you implore the person to put away his phone for a while.
I think that's the best option. If the person seemed not to listen, just ignore the person to avoid trouble or distraction. Sometimes, that incidence cause a lot of distractions if you pay attention to it. Ignoring such person after warning will be the best thing ever.
I hope this makes sense???