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I'm no expert, but I think Straczynski do pretty decent job... I think if there is something that JMS is good at, it's the arc story.
I was a fan of Babylon 5, but it was a love hate relationship. Sure JMS did a great job, but we were always left wondering if the stories could be better if JMS wasn't trying to do everything. He did (do them all) and it came out pretty well.
I'm no comicbook expert (see the wastebasket for that expertise) so I have no idea if he's been brutalizing Spiderman or keeping it going well, riding high on the cinematic successes.
So I say, what the heck, the guy's gotta make a living!