After having a look through the market place, there are some good, bad and ugly. I agree with the landscapes one especially since I am an en environment artist, and using a tool such as the terrain tool is as easy as chips with a little practice for a novice. With most of the marketplace assets these are mainly aimed at place holders and more in depth looks which can be great for concepts and alphas, but full release games should have some originality. Its fine to use a few assets which are just right for your project by final release, but most marketplace assets you will never see in a final release.
It all boils down to price and usage. A lot of things on the market place look quite good, but its down to the user/developer to put a price tag on what they expect. For me, and maybe many others some assets are really over priced, and some are under priced. One asset which really stuck out and i actually purchased is the Star FX starter kit. For 5 bucks, that what the marketplace should be about. Its an asset and can be used in even a AAA title! And for the price and versatility, the marketplace should have more assets like that, at that price.
What i would suggest is to literally have an unofficial marketplace like has been suggested, but that has to be regulated too. I think it would be a good idea to have a submission process where the asset is quickly checked out to make sure it works, then is immediately listed in the “unofficial market place” or Testing area. Epic could then see what is most popular and what is best to be featured in the “official” marketplace. That way everybody would have a lot more choice (choice is lacking at the moment and just a few assets in each category shows its limits to usage and game types using U4). I for one have many models which i could get up on the market place, but probably the same as others, the whole process is too time consuming for me.
Variety is the spice of life, and having more assets is better for the engine, for Epic, The asset creator and the Dev. For most games, there is not one asset devs can make any use of, and if they could there is not much of a choice in the marketplace.
Just my 2 cents 