The notion that the movies are "ruining Transformers as a whole" is what puzzles me here. I think we, as Transformers fans, owe a lot to those movies. They not only brought in piles of money, they also introduced Transformers to a new generation of people. Now, let's be honest here: the Unicron Trilogy cartoons were garbage. They had cool toylines and a great video game, but they did little in the sense of multimedia to attract new fans. Then come the movies. Those movies, you see, they're the reason we have all the stuff we have today. If it weren't for them, the franchise wouldn't be on the level it is now. Animated? Probably wouldn't last a season. War For Cybertron? Would have a much smaller scope. The precious Classics/Generations lines? Nope. And the Prime cartoon? Wouldn't even exist.
Michael Bay is not a good director in the traditional artistic sense. But he's good at what he does, which is making entertaining, action-packed films, and he has made himself and many others very rich with that work. Now let's be honest: with the exception of ROTF, were the TF movies so bad in terms of being a fun action movie? They had decent scripts (again, except ROTF), good action scenes, and in general, worked really well as popcorn flicks. And while it's fair to criticize any aspect of them - I'd be the first to do so - we shouldn't expect much more than that.
Love them or hate them, the movies do bring a massive benefit to the Transformers brand as a whole. Independently of their quality, they'll keep bringing in new fans, increasing toy sales and allowing the existence of better TF media all around.