I recently visited the Bubble Nebula, thought it was amazing.
The Crab nebula is pretty special too, although more so as you approach it over the final hundred or so ly but even when you are inside you get some pretty wild colours. ETA Carina was one I remember being disappointed by up close, all indications of it's famous 'double bubble' shape were absent, it was just a generic reddish whispy blob.
I think the attempts to replicate the shape & colours of real nebulae are really well done, the artificial colours are added in a way that seems a reasonable compromise between realism and what viewers expect based on IRL colour enhanced images of them.
There could be a lot more done with the proc gen nebulae though, they mostly all look like the same voxel rotated in different ways and there are far fewer on the far side of the galaxy (where everything is proc gen) compared to the variety of real ones on the bubble side. Some planetary nebulae are amazing though, and there are many unique shapes & colours (all are emission nebulae of course).
Nebulae are extremely... well nebulous

They are also truly enormous. That space engine vid shows views that seem more akin to flying through atmospheric cloud structures. They do look pretty though, perhaps we will get something more like that if thicker atmospheres and weather are eventually added.