If you've ever actually seen Infiniminer, it was actually an extremely different game than what Minecraft came to be. Infiniminer was a competitive game, where two different teams had to race to mine a quota of materials. It also had a class selection if I recall. The only thing you could argue is a "clone" is MC's creative/classic mode, which Infiniminer also had. also the base block concept, but doing that would be like calling Call of Duty a Doom clone.
FortressCraft (once it's released, not counting the current freebuild mode) is similar enough to be considered a clone in my opinion. The graphics style is identical and the objectives and gameplay are the same thing. But at least they're trying to make things different and acknowlege the inspiration from MC, the developer isn't afraid to say he was inspired by MC and wants to make his game what he always wanted MC to be.
And I respect that.
However, Total Miner: Forge is another story. It's an absolute shameless ripoff, in both graphics and gameplay. They also strictly avoid mentioning Minecraft's existence, it makes me sick.