Another project I've had to catch up on....
The individual bits and pieces (so of which are huge, like the parking lot) are very nicely done and show great realism. Also, the coaster layouts and general landscaping of the areas around the rides looks great. I think you're doing fantastic work here.
As Shyguy says, though, everything sits in an unfinished landscape. It's like butterflies pinned to white cardboard, beautiful objects on a sterile background which robs your excellent work of life. So I recommend, before building something else, go back and flesh out the surroundings of what you've already done. Airbrush the ground in a mottled pattern so it's not all monochrome green. Add some underbrush, flowers, fences, lights, bins, and benches. Smooth off that big cliff in the background where the level of the park is below the default terrain height in that corner of the map, then put trees on the resulting slope to make it blend with the background. That sort of thing.
