If we're going to talk quality, then Dark Knight was excellent. But Transformers 2, while having a lot more action, kinda fell with the plot. The Dark Knight had an outstanding plot, but while the action in the movie was brilliant, Transformers 2 was better.
If we're going to talk how much money the movie made, they're pretty close. I started collecting issues of Entertainment Weekly the week b4 the Oscars of 09, and started reading them a year before that. In each issue, there is a chart stating what movies in theaters made what, where, how much in the weekend, number of sites, and a rating. Transformers got a B, and if i remember DK got A or A+.
Anywho, the third Lord of the Rings movie; return of the king, was the highest and fastest grossing movie of all time, until the dark Knight came out, if i remember eventually making half a billion dollars. Transformers 2 has so far made 300 million, making it around the second highest grossing movie of all time.
The odd thing is the similarity. Both were sequels (if one remembers correctly, DK was a sequel to 2005's Batman Begins), extremely successful (100 million gross is considered successful), and the concepts behind the movies weren't created by a Hollywood writer, but by some guys writing comic books and making toys. (excellent toys)
So overall? Dark Knight beats Transformers in plot
Transformers beats dark knight in action
The best acted role of all time is Heath Ledger (bless him) as the Joker
And the hottest supporting character is Meghan (or megan) Fox.