Content, content, content...
As you all know, an engine is only as good as its content. Take a look at the old Half-Life 1 engine. Though it was very limited, the look of the game is - even today - quite good. The good textures (although they have a very low resolution) and the realistic lightning made HL look better than most games from that time. On the other hand, without good content, even the best engine can look crappy, look at some Unreal Engine based games like Mobile Forces, which had really ugly graphics, though the engine was far more capable. Today, the content users expect is at a level that takes very long to be achieved (just look at the Unreal Engine 3.0).
Content creation is becoming the next big bottleneck in 3D graphics. Well, why do I write that? Cause I’ll try to create a few (very few), high-quality assets for my engine, so I can showcase them a bit in the prototypes. Might be some time until I update the blog again, content creation takes time, plus I got loads to do.