I find that the ones I don't care for also happen to be the ones that stray too far from the original concept of the character.
Examples: Han Solo is a charismatic rogue who's fine with getting dirty. So this concept works with the original spirit of the character.
On the other hand ,Luke looks like a grizzled-veteran, which doesn't fit his character. In Star Wars, Luke is supposed to be a baby-faced youth, a "pure" character. Almost like Oliver Twist, someone who doesn't belong in the underworld, someone who was born of a higher-class/destiny. Luke is not a "dirty" character, he's royalty.
The problem with Boba Fett is similar. He's a clone of a genetically-perfect super-soldier. Does that look like the like build of a soldier? No, it's a good character, but it's not Boba.
The Stormtrooper looks better than the Star Wars version, but he doesn't look incompetent. A Stormtrooper has to be incompetent.