First off Don't Click This!

The following "Scientific" theories were either wholly unscientific or failed to pass scientific testing. Creationism/Intelligent Design can certainly be included in this list, though the political fight rages on...

Geocentrism [link] (Earth is the center of the universe - Replaced by Copernicus, which was improved by Kepler, then Newton, then Einstein)
Lamarckism [link] (Animals pass on traits developed during lifetime - Replaced by Darwin)
Spontaneous Generation [link] (Complex life spontaneously appears - Replaced by Pasteur)
Miasma Theory of Disease [link] (Disease is caused by "bad air" - Replaced by Germ Theory of Disease)
Rutherford Atomic Model [link] (Impermeable nucleus with orbiting electrons - Improved by Bohr's Model, which was improved by Electron Cloud Model)
Expanding Earth Theory [link] (The earth is growing radially causing continents to separate - Replaced by Plate Tectonics)
Alchemy [link] (Materials of the earth can be used for spiritual abilities - Replaced by Chemistry)
Astrology [link] (Motion of heavenly bodies directly affects human life - Replaced by Astronomy)
Phrenology [link] (Personality traits are related to the geometry of the head - Replaced by Psychology and other Neurosciences)

^{DISCLAIMER: Be careful with Wikipedia Links. Always bullshit check their sources.}

Why is Creationism/ID not a science? Because it lacks the study of anything mechanical. It uses mechanical sciences to search for forensic evidence. At best it's a study of forensics which has more in common with philosophy than any hard science. The creator is very loosely defined as nothing more than the external action which created whatever is being studied.

There is no study of how the creator created it -- just evidence of a creation. That, my friends, is forensics and is not inherently science but the application of science.

Whether there was/is a creator or not is irrelevant in scientific studies. If there was a creator, then all the evidence points to him using evolution to get here. If there was not a creator, then at some point, the building blocks of life sparked spontaneously and evolved into more survivable forms.