There's a lot here I could go into, but what much of it boils down to is that video games are a relatively young art/entertainment medium. Currently the medium is suffering having passed it's immature creative peak (where most of the possibilities of the medium are still being explored and technical limitations are rife--both factors leading themselves to early successes based more on luck and instinct than careful thought and application of design theory) but still being in the middle of hashing out a conceptual framework for itself so that it can proceed in a more developed and mature fashion.
What this says about games produced today is that they're being produced while the medium is in the dark Crappyfrankenclone Valley between early, spontaneous creativity and mature, sophisticated understandings. This means that many of those creating games do so without a solid understanding of what actually makes a game work and thus resort to either a) slicing bits off of various, successful, games and creating some horrid Frankengame in the hopes that it'll be 'creative' and sell; or b) cloning a successful game and hoping that better graphics/slight tweaks will sell.
Of course, there are still people who make good, successful, original games; but the number of them who do so through luck/spontaneous inspiration is growing smaller and is being replaced by game devs who have an increasingly solid grasp of what it is about their game that makes it good and why/how those parts of their game work.
Games won't stay crappy, it's just that for the moment we've exhausted most of the more obvious options and now need to invest some serious cogitation into the theory behind games.
Actually, it's kinda exciting, realising that the second wave of game design (where theory is king) is in the process of breaking around us and that we can be participants in cleaning up the legacy of the first wave (where innovation was trump).