Here's some food for thought.
Jet Set Radio Future has fantastic controls. This game bombed when it released, and was almost immediately sold as a free pack-in to the Xbox.
If I made a topic about why it isn't more popular, you wouldn't say "Because it controls poorly."
You'd consider a number of other factors...as you should here.
I'm of the belief that good games that don't sell are an issue of visibility, marketing, and demographics, in that order. That's just the cold reality of how the market works. In LBP's case (the original anyway), the only one of those factors that seemed to work against it was demographics, and even then, selling nearly 5 million copies indicates that there's SOME sort of audience there to work with. Sony made damn sure that people knew LBP existed, being aggressive with its pricing, constantly having it available for bundling by retailers, and, don't forget, GIVING AWAY the entire game for FREE after the whole PSN fiasco.As I said earlier, Sony most definitely tried to ram this game down people's throats.
I think what's more telling is what happened with the second game (and the PSP game, but I don't think that applies completely here). Without the advantages of incredibly aggressive marketing (still not sure why Sony eased off for the second game, there was no good reason to) and the visibility that comes from launching in the holiday season, the only thing it could rely on was whatever audience it built off the previous title. Apparently, that ended up being smaller than we thought, not that it doesn't still have some volume behind it.
Why the dropoff? Either most LBP1 purchasers were happy with just the first game, which is a valid possibility, or when all was said and done they just didn't care for the game enough to bother with the sequel. Either scenario is not good for the franchises's prospects.