Personally, I think the art of the old manga Transformers is really good(several translated issues found here:
http://www.tfarchive.com/comics/japanese/ ), and here's a couple highlights:
Can't talk of manga without my personal favorite one-shot character Guiltor!
Yeah, he appeared only in that one issue(Tranformers 2010 #4), and is quite possibly the most obscure character in the entire TF universe.
And I think the manga art of Trypticon is awsome, particularly here:
I daresay that's the best Trypticon art EVER. Hyper-detailed that the show could never match, unfortuneately.