I thought his Fantastic Four run was okay. Wasn't a big fan of his Avengers run, despite him expanding the line-up in a way I think made total sense (even if I didn't agree with every character). I tried his Secret Warriors and S.H.I.E.L.D. but quit after a bit...they just left me cold.
Hickman strikes me as a writer who has big ideas and loves to incorporate those ideas, but then just wallows in them, as nobody loves those big ideas more than Hickman. Snyder at DC has the same problem, I feel...huge world-views, but execution that caters to the world-views more than the characters inside of them.
As far what I'd like to see him work on now at Marvel...maybe some kind of fantasy comic, like going deep with Weirdworld or bringing back Crystar or something. Something that allows him to build an entire universe from (almost) scratch and do whatever he wants with it, but in a way that it has minimal impact to other Marvel books being published at that time.