I am a big fan of water-based tire dressings instead of more common silicone-based tire dressings. A silicone-based dressing will generally leave a shinier look that lasts considerably longer, but they really gunk up the tire and can have other negative effects over time. A water-based dressing will actually soak into the sidewall helping to condition the rubber and reducing the chances of slinging off.
I am currently using
Meguiar's Hyper Dressing diluted 1:1 with water. It gives a nice, somewhat shiny finish that doesn't look too synthetic or over the top to me. The only downside is that it is only available in gallon size containers which may take the average car owner forever to use up.
Another great option that is available in smaller sizes is
CarPro PERL. When used neat, it will leave a dark finish that has some shine to it. Since it is water-based you can dilute it with water to reduce shine if that suits your style better.
Product Review: CarPro PERL by Zach McGovern
Hope that helps!
Zach McGovern
Former Pro Detailer
Detailed Image Ask-A-Pro Blog Author