He does fine when he writes straight superheroics. His X-Men's a little unfocused, but his work in the Ultimate universe has been readable to excellent.
Ellis somehow has a reputation as a guy who hates superheroes, when it's simply that he pointed out that A) some parts of accepted superheroic canon like the skintight outfits are rather silly and B) they dominate the market to a ridiculous extent. Both things are true. Half the people who read it took those statments as an attack against the genre, though, because people are stupid.