I've seen Orlando Bloom in other movies. I have yet to see him display much talent; in fact, I always think that he's barely distingishable from the scenary. Johnny Depp ran circles around him in Pirates of the Caribbean[i] and he didn't even seem to notice it. Than again, Johnny Depp is a great actor. In Kingdm of Heaven[i], I thought the film would have been improved if he wasn't in it.
Legolas never really did anything other than look pretty and do CG-assisted stunts that no other elf seemed to be capable of (which makes no sense really; these guys are thousands of years old, and they can't beat an army of Uruk-Hai who are only a few weeks old?). Basically, Legolas was the pretty boy of the party, who's hair was never mussed, who never runs out of arrows (where does he get them?) as opposed to Aragorn, who always looked like he slept in a muddy ditch and who takes a few blows over the course of the films (not always neccessary ones either). Legolas is to appeal to the type of people who like romance novel covers.
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"Meet the new boss, same as the old boss"
"It's all right Ma, I'm only sighing"