I was curious and decided to count up the number of original vs. licensed suggestions in this thread. I tried not to count suggestions twice, and "upvotes" of suggestions were not counted. I will say that there was some ambiguity here and there (e.g., travel the country vs. travel the world, funfair vs. amusement park, etc.). Whatever. I wasn't very detailed about it, so take this count with a grain of salt.
Original Theme suggestions: 65
Licensed Theme suggestions: 42
Sequel of an original suggestions: 3
Kind of interesting results. The fact that ~40% of all suggestions in a thread asking for original themes were actually licensed is very telling. As some one else mentioned, maybe the demand for original themes isn't as high as we think it is.