The phrase "certain charm" means that something or someone has a specific and unique appeal that is difficult to explain or put into words. Full definition
At the very least the character models look good, not great like Final Fantasy XII or anything like that, but they have their own certain charms. (gamingnexus.com)
Even though the newer version made a lot of improvements to the game overall, the original just has certain charms unique to it, perhaps on account of being a product of its time. (poisonmushroom.org)
After all, he does have a certain charm and performed better than his boss. (firstthings.com)