first of all, i don't think a comparison of this sort should be even made.
They wouldn't fight, and considering boromir's ..life extension, they never will either.
They're on different skills. Boromir is good with a sword and shield, legolas with the bow and knifes. And the elves are quicker. So yeah, i'd bet on legolas.
But this is like comparing frodo with sam..or...dunno what
if boromir would get close to legolas, which I think is very likely legolas would die, boromir was a very tough and brilliant warrior as ush already stated, he wouldn't die of a few shots (as we have seen in the fellowship) if boromir would get legolas in reach of his blade I think legolas would end up being a pile of mudd, chances are great that boromir would die after that one