The first isn't all that great on a rewatch either. I can at least remember the plot of Avatar. Transformers 1 was about a pair of glasses, a box that turns things into robots, and Megan Fox being attractive. Anthony Anderson also ate a plate of donuts for some reason.

While I agree that James Cameron is overrated, I wouldn't say he is a bad director and I certainly wouldn't rank him with Michael Bay.

Cameron's Avatar movies are not overly original and some of the plot points are rather shallow, but at least the plot is coherent and he does try to push creative boundaries. Bay's Transformer movies have no coherent plot and exist purely for spectacle and explosions. Bay routinely reuses shots in his movies, so he's not even pushing boundaries on his spectacle.

Just because both franchises have an abundance of CG doesn't make them the same in quality.