If I were doing the same build two months from now, probably not. But I don't think the new APUs are shipping in any commercially available real quantity yet, and many ryzen socket motherboards do not yet support 4K at 60Hz for their onboard HDMI outputs.
For 3D gaming (not video decode GPU-assist performance), to me, neither the gt1030 or the ryzen 2400G look like they have acceptably smooth framerates (45-60 fps) at 1080p high settings:
According to heise/c't magazine[1] (highly respected German tech publication), the Vega-based APUs support HDMI 2.0 even if the motherboards only advertise HDMI 1.4 support, as the pins are directly routed from the APU package. DisplayPort 1.2 works for 4K@60Hz as well of course. I suppose there's a risk the motherboard traces might be too low quality to carry HDMI2 signal speeds on some boards; hopefully board makers will revalidate and update specs for their boards. On the other hand, it may be worth waiting the 5-8 weeks until 400 series chipset boards come out which will presumably be designed with Ryzen G in mind.
Specifically in the 1500x price point, the r5 2400G seems to have performance on par with a gt1030.
https://www.anandtech.com/show/12425/marrying-vega-and-zen-t...