Nothing complicated is exactly like anything else complicated. To claim something is not Earthlike because it does not match some arbitrary personal standard of similarity simply sounds dogmatic. It is obvious that for a variety of reasons Mars is the most "Earth-like planet" in our solar system.

Mars is also obviously very different from Earth and assuming similar features are due to similar processes can be a trap. There is nothing wrong however with using this as a working assumption and looking for further supporting evidence. One way or another as data builds up the real cause will usually be found. Of course, data supporting alternative causes should also be searched for when they match the data accumulated so far.

No knock intended on your theories Nick.

Regards,
Mark