Welcome new guy!
The director of The Terminator? Frequently referred to as one of the best sci-fi movies ever, its antagonist one of the best bad guys ever? The director of T2? Frequently referred to as one of the best sequels ever, as well as an absolute technical milestone? These movies transcend so dramatically anything that Bay has ever done that the comparison, in whatever form to the Bad Boys director, is a strange one.
Would you argue that Alien is style, flash but little substance? I'll wager that you wouldn't. So is Aliens a more apt example then of style, flash but little substance? One of the best sequels ever, expanding Scott's universe in valid and intriguing ways. True, these movies exist primarily to thrill and frighten, but we're absolutely nowhere near a "leave your brain at the door" sort of thing. Their substance is the brilliance in how they're directed, in their premises and how the feelings they elicit from the audience go far beyond "solid, mindless timewaster."
Even Titanic is a huge labour of love for the director. He wasn't interested in the story of Jack and Rose, but in the ship herself and there is great substance in how majestically she's been framed and how accurate Cameron's depiction of her sinking is.
I think Cameron's a great storyteller by the way, but I agree that True Lies and Avatar are his weakest efforts.