It's hard to put them in order, because the context is often more important than the particular word. For example, "superb" has a very strong meaning in formal contexts, but in casual conversation, the meaning is less impressive. Also, context will sometimes determine which words make sense, and which ones would sound odd. Personally, with no context given, I would put them (ROUGHLY) in this order: incredible (most impressive) superb amazing fantastic excellent wonderful great nice (least impressive) I didn't put "awesome" on my list, because it can have two very different meanings, depending on context. In a formal context, where it means "awe-inspiring," it belongs at the top of the list. Something "awesome" is intensely, overwhelmingly impressive. However, in casual conversation, the word "awesome" can be used to simply mean "good" or "cool." If someone says that something is "awesome," you'll need to listen to their intonation, or pay attention to the context or the rest of their sentence, to figure out whether they mean the word in a casual or a more serious way.

nice>great>awesome>excellent>amazing>fantastic>wonderful>incredible>superb in my opinion