I think it's important to clarify the requirements. He says "software for creating terrains that looks more realistic to natural world". If that's really the focus, then much of the list becomes less relevant and many others should be added, e.g. Geocontrol. If he wants a full rendering package like TG2 or Vue, then World Machine does indeed not belong. Further, if terrain generation and editing is indeed the focus, then the next question is what will the terrain be used in/for. Depending on the target application, the output formats of your terrain editor will matter more.
- Oshyan