Your lack of gloss maps is really killing the final quality of these assets, and you are not taking full advantage of Marmoset's PBR pipeline. You are getting these even highlights across all your surfaces which is making them look a bit dated. Also in PBR workflow you shouldn't be baking your AO into your albedo maps,…
I think this should help out http://www.marmoset.co/toolbag/learn/pbr-practice In this case... diffuse = albedo roughness = microsurface specular = reflectivity
That's one of the driving factors behind the shift to pbr in games.It helps to ensure consistency. Whole pipelines are now built around Substance Designer, for instance.