Which do you think is the best live action Transformers film?

Hmmm...
I might be in the minority, but I actually really enjoy the TF films.
Surely, they're big and explosions and dumb, but that's what I expect so never get disappointed.
I actually love ROTF (it was my favourite film for a long time), so from best to worst for me would be ROTF, DOTM, AOE, TFTM.

I think AOE suffered from being too long, especially at the end, because I felt it's human characters were more interesting (though I always find myself laughing at Sam's parents).
My biggest issue with them is the confusing fight scenes and the lack of Megatron-first one he is frozen for most of the film, second we have the Fallen, third we have him being Sentinel's B***h, and 4 he just says "Get me the Seed!"

Then again, I guess I'm the target market :p:p

Yeah, I personally never understood how anybody could be "disappointed" by the movies. Unless you don't know who Michael Bay is, you're getting exactly what you'd expect.