There are two separate things that play.
First, the background itself is animated, which plays constantly. Flashblocker prevents the Cities Skyline background animation, but does nothing to Unwritten Tales.
Second, the ads can create a takeover pop-up video that will start playing upon activation. With Unwritten Tales, you actually have to click on the activation area to trigger this pop-up. With Cities Skyline, simply letting your mouse rest within the large activation area for a few seconds will cause it to trigger.
In regards to the second issue, Unwritten Tales is ‘better’ than Cities Skyline, because at least it requires direct action by the user to trigger Unwritten Tales’s takeover pop-up. Mind, Unwritten for a background ad has an insanely high CPU load, so it isn’t that either is good. It is rather sad that RPS seems to be aiming at being the worst of gaming sites when it comes to ads.